THE INFLUENCE OF DATE OF HATCH 0N LENGTH OF LAY, EGG SIZE DISTRIBUTION AND SELECTED EGG QUALITY CHANGES IN A COMMERCIAL LAYING FLOCK Thesis for the Degree of Ph. D. MICHIGAN STATE UNIVERSITY FLOYD W. HICKS 1961 WWIIIIIIIIIIIIII L 310788 3112 IIIIIIII 31 n11 This is to certify that the thesis entitled The Influence of Date of Hatch on Length of Lay, Egg Size Distribution and Selected Egg Quality Changes in a Commercial Laying Flock presented by Floyd W. Hicks has been accepted towards fulfillment of the requirements for Ph.D. Poultry Science degree in ,) / (IT / I / ~v.1(HL1I~1 ~ 1;.» 7/ ‘, Major professor 7 Date May 18, 1961 0—169 MSU LIBRARIES RETURNING MATERIALS: Piace in book drop to remove this checkout from your record. FINES wiII be charged if book is returned after the date stamped beIow. ULIIDB‘E 5x ._.—_ _—_—__—— -—., _., THE INFLUENCE OF DATE OF HATCH ON LENGTH OF LAY, EGG SIZE DISTRIBUTION AND SELECTED EGG QUALITY CHANGES IN A COMMERCIAL LAYING FLOCK By Floyd N. Hicks AN ABSTRACT OF A THESIS Submitted to Michigan State University in partial fulfillment of the requirements- for the degree of DOCTOR OF PHILOSOPHY Department of Poultry Science 1961 C~ ABSTRACT THE INFLUENCE OF DATE OF HATCH ON LENGTH OF LAY, EGG SIZE DISTRIBUTION AND SELECTED EGG QUALITY CHANGES IN A COMMERCIAL LAYING FLOCK by Floyd W. Hicks The recent and rapid expansion of the poultry indus- try plus the accompanying technological changes have tended to obscure many important egg production problems. These problems confront those poultrymen who replace their flock annually or replace their flock at periodic interVals throughout the year. When utilizing present-day strains of laying hens, the pertinent question arises: "Are there differences in the optimum length of lay if economic considerations have included the hatching date?" The practical consideration of seasonal hatching dates by the commercial poultryman should result from an analysis of: 1. The length of lay. 2. The rate of lay. 5. The egg size distribution. 4. The changes in egg quality by age of birds. A commercial poultry farm in Michigan was the site for the investigation reported herein. The management brooded chicks at various times of the year due to the size of the operation. Floyd W. Hicks The commercial strains of laying hens used were Heisdorf & Nelson ("H & N") and "Hylines." The bimonthly hatching seasons utilized were: February 1, 1958; April 1, 1958; June 1, 1958; August 1, 1958; October 1, 1958 and December 1, 1958. Similar hatching dates were used in 1959. Generally accepted managerial practices were em- ployed by the Operator in the brooding and rearing pro- cedures regarding housing space, lighting, disease control and nutrition. Pullets were housed in pens in various numbers, in keeping with the housing facilities on the farm. The num- ber of birds tested varied from 750 to 2400 pullets. In- dividual pens of birds, representing the different hatch- ing dates, were kept over for the extended lay period (six months of extra lay, to a total of 24 months of lay). The birds were 50 months of age at the end of the period. The total egg production, seasonal egg size distri- bution, and selected egg quality factors were measured for the females tested which were hatched at different seasons of the year and retained for the extended-lay test period. Representative pens of layers of the various strains were randomly selected for computations of seasonal egg size distribution. The egg size distribution, expressed in total numbers of dozens of eggs produced by the differ- ent strains of layers, was calculated from the egg P§W~ Floyd W. Hicks production data. Hatching date effects were investigated relative to albumen quality, shell thickness and blood spot incidence. Daily egg production records were kept by the farm poultryman, but two-day bi-weekly data were gathered by the investigator. All possible comparison combinations were statis- tically analyzed by strains, by hatching dates and within years. Comparisons were also made between strains and be- tween years when similar hatching dates were involved. All data were subjected to an analysis of variance and Duncan's Multiple Range Test. *The analyses of the data, under the particular en- vironmental conditions of this study, have indicated that satisfactory egg production may be expected from females hatched at any time of the year. This study showed that the factor of age at sexual maturity did affect the curve of egg size distribution. Age at sexual maturity did not affect the total numbers of eggs produced. No consistent seasonal hatch effects on total egg production could be expected on the basis of season of hatch alone. Location effects within the poultry farm were not significant. Egg weight distributions according to hatch date were important. Egg size decreased in the summer months in this investigation of the extended lay periods. The differences in egg weight distribution between strains were even more evident. IIIIIIIIIIIIIIIFEIIEIIIIIIIIII-I--_____________________ ‘3 .‘\ E02 silo chic}: : rat-l- p. ,-Y\ U. Us; Floyd N. Hicks Albumen quality and shell thickness were not af- fected by hatching date. The incidence of blood spots were significant in the very late summer, fall and winter months. It can be concluded that, given the modern laying pullet, it is best for the poultryman to schedule his chick starting dates according to his own convenience rather than on a set caiendar pattern. THE INFLUENCE OF DATE OF HATCH ON LENGTH\ OF LAY, EGG SIZE DISTRIBUTION AND SELECTED EGG QUALITY CHANGES IN A COMMERCIAL LAYING FLOCK By Floyd W. Hicks c A THESIS Submitted to Michigan State University » in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Poultry Science 1961 I! “I Dr. constr 9. «\U ad .s.‘ C ACKNOWLEDGEMENTS The author wiShes to express his appreciation to Dr. H. C. Zindel, Professor of Poultry Science, under whose direction this study was conducted, and to Dr. L. E. Dawson, Associate Professor of Poultry Science. Their interest in this study and their effort in direction, and the supplying of materials and facilities were greatly appreciated. The writer is indebted to Drs. Merle Esmay and Henry Larzelere for their helpful suggestions and their constructive review of this thesis. The author is also sincerely grateful to Dr. L. R. Champion for his encourage- ment, advice, and direction in planning the statistical analyses. An expression of sincere gratitude is extended to Ir. and Mrs. Harry Burns for provision of data, facilities, and encouragement for this study. Appreciation is also .acknowledged to Dr. R. G. Wheeler and those numerous asso- <2iates who made visits to the commercial poultry farm to Egather data or offer assistance. Finally, the writer is indebted beyond expression tn: his wife, Dorothy, for her encouragement, sacrifice, Eind patience during this strenuous period of study and research. ii p was $6710- 9- .h :4 II. III. IV. V. VI. VII. VIII. IX. ACKNOJLEDGEMENTS . TABLE OF CONTENTS TABLE OF CONTEIITS O O I O O O I O C O O O O O 0 LI ST OF TABmS . o o 0 o a a c o I o o o O 0 0 LIST OF FIGUES. I O O l O I I o I o O I C l I 0 LIST OF APPENDICES O O I C O n O o O I I O O O IIITRODUCTION I O C l O D O O I C O O I O I O . REVIEOJ OF LI TERATUE I O O O O I O O O O C O 0 MATERIALS AND METHODS. . . . . . . . . . . . . RESULTS. I O C O 0 C O C O O C 0 I O O O C O O Hatching season comparisons \OCDQOW \n #WNH Strain I February versus April hatching season February versus June hatching season . February versus August hatching season February versus October hatching sea- $011- 0 o a O 0 I o l o o o e I o I o 0 February versus December hatching sea— son. I O I O O C O O O O O C O I O O 0 April versus June hatching season. . .' April versus August hatching season. . April versus October hatching season . April versus December hatching seaSOn. June versus August hatching season . . June versus October hatching season. . June versus December hatching season . August versus October hatching season. August versus December hatching season October versus December hatching sea— son. 0 C O O O I 0 O I O O O O O O O . Strain II April versus August hatching season. . April versus December hatching season. August versus December hatching season iii Page ii iii xi xiii 28 41 TABLE OF CONTENTS (Continued) Page Strain III . February versus April hatching sea- SOD. I I I o I I o O I o o o o I I I I 97 . February versus June hatching season . 97 . February versus August hatching sea- son. 0 O O O C . C O O C I O I O O O . April versus August hatching season. . June versus August hatching season . l 2 5 4. April versus June hatching season. . I 97 2 : Strain IV 1. February versus April hatching season. 98 X. DISCUSSION . . . . . . . . . . . . . . . . . . 170 XI. CONCLUSIONS. . . . . . . . . . . . . . . . . . 182 XII. BIBLIOGRAPHY . . . . . . . . . . . . . . . . . 186 XIII . QPEIIDIX I O O O O O O I O I C O I O O O C I O 191 iv Table 1. IO. 11. 12. 15. LIST OF TABLES The Average Hen-day Egg Production of Chickens Hatched at Bimonthly Intervals. Strain I. . . The Average Hen-day Egg Production of Chickens Hatched at Bimonthly Intervals. Strain II . . The Average Hen-day Egg Production of Chickens Hatched at Bimonthly Intervals. Strain III. . The Average Hen-day Egg Production of Chickens Hatched at Bimonthly Intervals. Strain IV . . Analysis of Variance of Average Hen-day Egg Production for Chickens Hatched at Different Seasons.* Strain I . . . . . . . . . . . . . . The Results of Statistical Analyses of Egg Production Means for Chickens Hatched at Dif- ferent Seasons. Strain I. . . . . . . . . . . Analysis of Variance of Average Hen-day Egg Production for Chickens Hatched at Different Seasons. Strain II. . . . . . . . . . . . . . The Results of Statistical Analyses of Egg Production Means for Chickens Hatched at Dif- ferent Seasons. Strain II . . . . . . . . . . Analysis of Variance of Average Hen-day Egg Production for Chickens Hatched at Different Seasons. Strain III . . . . . . . . . . . . . The Results of Statistical Analyses of Egg Production Means for Chickesn Hatched at Dif- ferent Seasons. Strain III. . . . . . . . . . Analysis of Variance of Average Hen-day Egg Production for Chickens Hatched at Different Seasons. Strain IV. . . . . . . . . . . . . . The Results of Statistical Analyses of Egg Production Means for Chickens Hatched at Dif- ferent Seasons. Strain IV . . . . . . . . . . The Average Hen-day Egg Production of Strain I Females Hatched on April 1, 1958 and Housed in Different Pens . . . . . . . . . . . . . . . . V Page 99 100 101 102 110 110 111 111 112 112 115 115 114 Table 14. 150 16. 17. 18. 19. 20. 21. 22. 25. 24. LIST OF TABLES (Continued) Page Analysis of Variance of Average Hen—day Egg Production for Strain I Females Hatched on April 1, 1958 and Housed in Different Pens . . 115 The Results of Statistical Analyses of Egg Production Means for Strain I Females Hatched on April 1, 1958 and Housed in Different Pens. 115 The Average Hen-day Egg Production of Strain I Females Hatched on June 1, 1958 and Housed in Different Pens. . . . . . . . . . . . . . . 116 Analysis of Variance of Average Hen-day Egg Production for Strain I Females Hatched on June 1, 1958 and Housed in Different Pens. . . 117 The Results of Statistical Analyses of Egg Production Means for Strain I Females Hatched on June 1, 1958 and Housed in Different Pens . 117 The Average Hen-day Egg Production of Strain I Females Hatched on October 1, 1958 and Housed in Different Pens . . . . . . . . . . . 118 Analysis of Variance of Average Hen-day Egg Production for Strain I Females Hatched on October 1, 1958 and Housed in Different Pens . 119 The Results of Statistical Analyses of Egg Production Means for Strain I Females Hatched on October 1, 1958 and Housed in Different Pens o I I o I I I o o I I I o I o I o o I o I 119 The Average Hen—day Egg Production of Strain III Females Hatched on June 1, 1959 and Housed in Different Pens. . . . . . . . . . . . . . . 120 Analysis of Variance of Average Hen—day Egg Production for Strain III Females Hatched on June 1, 1959 and Housed in Different Pens. . . 121 The Results of Statistical Analyses of Egg Production Means for Strain III Females Hatched on June 1, 1959 and Housed in Differ- ent Pens . . . . . . . . . . . . . . . . . . . 121 vi Table 25. 26. 27. 28. 29. 50. 31. 52. 55. 54. 55. LIST OF TABLES (Continued) Page The Average Hen-day Egg Production of Strain IV Females Hatched on February 1, 1959 and Housed in Different Pens . . . . . . . . . . 122 Analysis of Variance of Average Hen-day Egg Production for Strain IV Females Hatched on February 1, 1959 and Housed in Different Pens . . . . . . . . . . . . . . . . . . . . 125 The Results of Statistical Analyses of Egg Production Means for Strain IV Females Hatched on February 1, 1959 and Housed in Different Pens . . . . . . . . . . . . . . . 125 The Percentage of Jumbo Eggs Produced by Females Hatched at Different Seasons of the Ye ar I I I I I I I I I I I I I I I I I I I I l 24 The Percentage of Extra—large Eggs Produced by Females Hatched at Different Seasons of the Year I I I I I I I I I I I I I I I I I I 126 The Percentage of Large Eggs Produced by Females Hatched at Different Seasons of the Ye ar I I I I I I I I I I I I I I I I I I I I l 28 The Percentage of Medium Eggs Produced by Females Hatched at Different Seasons of the Ye ar I I I I I I I I I I I I I I I I I I I I l 50 The Percentage of Small Eggs Produced by Fe- males Hatched at Different Seasons of the Year I I I I I I I I I I I I I I I I I I I I 152 The Percentage of Peewee Eggs Produced by Females Hatched at Different Seasons of the Ye ar I I I I I I I I I I I I I I I I I I I I l 54 The Percentage of Undergrade Eggs Produced by Females Hatched at Different Seasons of the Year I I I I I I I I I I I I I I I I I I 156 The Distribution, in Percentage, of Egg Weights Recorded in Two-week Intervals for Females Hatched on February 1, 1958 . . . . 157 vii LIST OF TABLES (Continued) Table Page 56. The Distribution, in Percentage, of Egg Weights Recorded in Two—week Intervals for Females Hatched on April 1, 1958 . . . . . . 159 57. The Distribution, in Percentage, of Egg Weights Recorded in Two-week Intervals for Females Hatched on June 1, 1958. . . . . . . 141 58. The Distribution, in Percentage, of Egg » Weights Recorded in Two—week Intervals for Females Hatched on August 1, 1958 . . . . . 145 59. The Distribution, in Percentage, of Egg Weights Recorded in Two-week Intervals for Females Hatched on October 1, 1958 . . . . . 145 40. The Distribution, in Percentage, of Egg Weights Recorded in Two—week Intervals for Females Hatched on December 1, 1958. . . . . 147 41. The Haugh Unit Scores for Eggs Laid by Chickens Hatched at Different Seasons of the Year. (By Age of Birds) . . . . . . . . . . 149 42. The Haugh Unit Scores for Eggs Laid by Chickens Hatched at Different Seasons of the Year. (By Similar Date of Sample) . . . . . 151 45. The Shell Thickness of Eggs Laid by Chickens Hatched at Different Seasons of.the Year. (By Age of Birds). . . . . . . . . . . . . . 155 44. The Shell Thickness of Eggs Laid by Chickens Hatched at Different Seasons of the Year. (By Similar Date of Sample). . . . . . . . . 155 45. The Percentage of Blood Spots Found in Can- dled Eggs Laid by Females Hatched at Differ- ent Seasons of the Year. . . . . . . . . . . 157 46. The Blood Spots Found in Broken—out Eggs Laid by Females Hatched at Different Seasons of the Year. (By Age of Birds). . . . . . . 159 47. The Blood Spots Found in Broken—out Eggs Laid by Females Hatched at Different Seasons of the Year. (By Date of Sample). . . . . . 160 viii Table 4'86 49. 50. 51. 52I 55. 54. 55. 56o 57. 58o 59. 60. LIST OF TABLES (Continued) The Monthly Cumulative Egg Production of Two Commercial Strains of Females Hatched at Dif— ferent Seasons of the Year . . . . . . . . . . The Monthly Cumulative Egg Size Distribution of Strain I Females Hatched on February 1, 1958 I I I I I I I I I I I I I I I I I I I I I The Monthly Cumulative Egg Size Distribution of Strain I Females Hatched on April 1, 1958 . The Monthly Cumulative Egg Size Distribution of Strain II Females Hatched on April 1, 1958. The Monthly Cumulative Egg Size Distribution of Strain I Females Hatched on June 1, 1958. . The Monthly Cumulative Egg Size Distribution of Strain I Females Hatched on August 1, 1958. The Monthly Cumulative Egg Size Distribution of Strain II Females Hatched on August 1, 1958 The Monthly Cumulative Egg Size Distribution of Strain I Females Hatched on October 1, 1958 The Monthly Cumulative Egg Size Distribution of Strain I Females Hatched on December 1, 1958 I I I I I I I I I, I I I I I I I I I I I I The Monthly Cumulative Egg Size Distribution of Strain II Females Hatched on December 1, 1958 I I I I I I I I I I I I I I I I I I I I I The Monthly Cumulative Dozens of Jumbo Eggs Laid by Two Commercial Strains of Females Hatched at Different Seasons of the Year . . . The Monthly Cumulative Dozens of Extra—large Eggs Laid by Two Commercial Strains of Females Hatched at Different Seasons of the Year . . . The Monthly Cumulative Dozens of Large Eggs Laid by Two Commercial Strains of Females Hatched at Different Seasons of the Year . . . ix Page 161 162 162 165 165 164 164 165 165 166 166 167 167 .n v I}. A L ~n / I“ :71 1:“ 25 r: r C r C n O #4.“,w‘ .1.- v Table 61. 62. 63. 650 LIST OF TABLES (Contined) The Monthly Cumulative Dozens of Medium Eggs Laid by Two Commercial Strains of Females Hatched at Different Seasons of the Year . . The Monthly Cumulative Dozens of Small Eggs Laid by Two Commercial Strains of Females Hatched at Different Seasons of the Year . . The Monthly Cumulative Dozens of Peewee Eggs Laid by Two Commercial Strains of Females Hatched at Different Seasons of the Year . . The Monthly Cumulative Dozens of Undergrade Eggs Laid by Two Commercial Strains of Fe- males Hatched at Different Seasons of the Ye ar I I I I I I I I I I I I I I I I I I I I Estimated Receipts from Eggs During Selected Periods. . . . . . . . . . . . . . . . . . . Page 168 168 169 169 181 Figure 1. 10. 11. 12. 15. 14. 15. LIST OF FIGURES Percentage of total Michigan farms report- ing chickens (1954 U.S. Census of Agricul— ture I I I I I I I I I I I I I I I I I I ‘I I Egg production per farm, Michigan, 1925- 1950, (A ricultural Marketing Service, UISIDIAI I I I I I I I I I I I I I I I I I I Eggs laid per average Michigan layer kept during selected years, 1925-1959. . . . . . . Monthly egg production and egg prices for the North Central Region in 1925-1929 . . . . Monthly egg production and egg prices for the North Central Region in 1950- 1954 . . . . The average hen-day egg production of chick- ens hatched on February 1, 1958 . . . . . . . The average hen-day egg production of chick- ens hatched on April 1, 1958. . . . . . . . . The average hen-day egg production of chick- ens hatched on June 1, 1958 . . . . . . . . . The average hen-day egg production of chick- ens hatched on August 1, 1958 . . . . . . . . The average hen-day egg production of chick- ens hatched on October 1, 1958. . . . . . . . The average hen-day egg production of chick- ens hatched on December 1, 195 . . . . . . . The average hen-day egg production of Strain I Chickens hatched at bimonthly intervals . . The percentage of jumbo eggs produced by fe- males hatched at different seasons of the year. I I I I I I I I I I I I I I I I I I I I The percentage of extra-large eggs produced by females hatched at different seasons of the ye ar I I I I ‘ I I I I I I I I I I I I I I I The percentage of large eggs produced by fe— males hatched at different seasons of the year xi Page 10 12 13 105 104 105 106 107 108 109 125 127 129 LIST OF FIGURES (Continued) Figure Page 16. The percentage of medium eggs produced by fe- males hatched at different seasons of the year. I I I I I I I I I I I I I I I I I I I I 151 17. The percentage of small eggs produced by fe- males hatched at different seasons of the year. I I I I I I I I I I I I I I I I I I I I 155 18. The percentage of peewee eggs produced by fe- males hatched at different seasons of the yearl . I I I I I I I I I I I I I I I I I I I 135 19. The distribution, in percentage, of egg weights recorded in two-week intervals for females hatched on February 1, 1958 . . . . . 158 20. The distribution, in percentage, of egg weights recorded in two-week intervals for females hatched on April 1, 1958. . . . . . . 140 21. The distribution, in percentage, of egg weights recorded in two-week intervals for females hatched on June 1, 1958 . . . . . . . 142 22. The distribution, in percentage, of egg weights recorded in two-week intervals for females hatched on August 1, 1958 . . . . . . 144 25. The distribution, in percentage, of egg weights recorded in two-week intervals for females hatched on October 1, 1958. . . . . . 146 24. The distribution, in percentage, of egg weights recorded in two-week intervals for females hatched on December 1, 1958 . . . . . 148 25. The Haugh unit scores for eggs laid by chick- ens hatched at different seasons of the year (by age of birds) I I I I I I I I I I I I I I 150 26. The Haugh unit scores for eggs laid by chick- ens hatched at different seasons of the year (by similar date of sample) . . . . . . . . . 152 27. The shell thickness of eggs laid by chickens hatched at different seasons of the year (by age of birds) I I I I I I I I I I I, I I I I I 1% xii Figure 28. Table LIST OF FIGURES (Continued) Page The shell thickness of eggs laid by chickens hatched at different seasons of the year (by similar date of sample) . . . . . . . . . . . 156 LIST OF APPENDICES Page Memorandum of understanding between the Michigan Agricultural Experiment Station and Harry Burns, Inc., a cooperating egg PrOducerO O O O O O O O O I O O O O O O O O O 191 Laying flock record card. . . . . . . . ; . . 195 Two—day egg grading record and summary card . 196 Two-week summary form of production factors . 197 Egg grading record card . . . . . . . . . . . 198 Egg quality records . . . . . . . . ... . . . 199 Individual pen identification of duplicated strains of birds used in location analysis. . 200 Monthly outside temperature ranges at Flint, LliChigan, 1958. O O O O O O O O O O O I O O O 20]- xiii INTRODUCTION At the present time, the commercial poultryman is faced with narrowed margins and reduced income. There- fore, it becomes important that each poultryman scrutinize the effects of his management practices on production and make the proper managerial decisions accordingly. The re- cent and rapid expansion of the poultry industry, plus the accompanying technological changes that have confronted those individuals specializing in the production of eggs, have tended to obscure many important production problems. Poultry managerial problems could become very troublesome in the future if apprOpriate adjustments are not made. Recent trends in the poultry industry in Michigan lindicate that egg production is being concentrated on fewer farms with larger production units. Concurrent with these changes has been the introduction of "contract" poultry production and/or integration of the individual poultry farm with large commercial concerns. With larger numbers of laying birds, the use of improved strains of laying hens, better rations, the adOp- tion of complex disease control programs, and the wide- SDread use of labor-saving mechanical equipment, it is vital that accurate, up—to-date data be obtained for costs of egg production and net returns. This is particularly important for those poultrymen who replace their flocks - 1 _ once a year or for those individuals who partially replace their flocks at periodic intervals throughout the calendar year. From an economic standpoint, using present-day strains of laying hens, the pertinent question arises: "Are there differences in the optimum length of lay if con- siderations include the month of hatching chicks or time of rearing pullets?" One approach to the problem would be to determine the relationship between month of batch and total egg production for egg-strain chickens kept through 24 months of lay. Egg size distribution would also have a bearing on the problem since egg size affects gross income and net returns. Poultrymen have long been aware of seasonal fluctu- ations in egg prices. The generally accepted recommenda- tion to the egg producer has been that he should schedule the time of starting his chicks so that peak egg production and favorable egg size are obtained during the period when egg prices are relatively high. It is understandable, therefore, to presume that a study of the seasonal costs and returns should materially aid in explaining the advan- tages and disadvantages of hatching at various seasons of the year. Further, such a study would help the poultrymen to plan an egg production prOgram such that he could take full advantage of the seasonal price changes which occur for eggs of Various weights. It has become increasingly apparent in the egg- producing phase of the poultry industry that poultrymen must consider the rising costs of rearing replacement pul- lets to sexual maturity. If the poultryman can profitably keep his laying hens beyond the normal l2-month laying year, it is understandable that he will materially reduce expenses. It would be economically advantageous for the poultryman to adopt this practice of keeping layers for this extended laying period, if he could not replace the old hens with pullets profitably. Considerations should be given to: (a) the price of the salvage hens, (b) the cost of rearing the pullets to maturity, (c) the alternate use of the pullet housing facilities, and (d) the annual depreciation of the rearing equipment with respect to the limited use of the equipment. Therefore, it has been suggested that the practical consideration of seasonal hatching dates by the commercial poultryman should become an analysis of: l. The length of lay. 2. The rate of lay. 3. The egg size distribution. 4. The timing of hatching dates or the purchase of day-old chicks. All of these factors must be considered in relation to costs and returns to the producer. The null hypotheses formulated for purposes of this study are as follows: (1) (2) (3) There are no significant differences in one or more of the economically important traits asso- ciated with total egg production between hatches of chicks brooded, reared, and housed at dif- ferent times of the year. There are no significant differences in egg size distribution between hatches of chicks brooded, reared, and housed at different times of the year. There are no significant differences between the egg quality factors of shell thickness and interior quality as measured in Haugh units be- tween hatches of chicks brooded, reared, and housed at different times of the year but kept beyond the normal laying period. REVIEW OF LITERATURE Trends in the Poultry Industgy In Michigan, the production of eggs constitutes the major portion of the poultry industry. The estimated gross i sented ncome from Michigan poultry products in 1959 as pre- by the Michigan Department of Agriculture Coopera- tive Crop Reporting Service is as follows: Estimated Gross Incogg Chickens 3 5,596,000 Turkeys 5,711,000 Commercial Broilers 5,542,000 Eggs 58,246,000 Total 3 48,895,000 A further elaboration of poultry statistics from the same source indicates that the income from eggs has dropped in the past seven years: nggi Gross Income, Eggs Gross Income, Chickens 1955 3 65,457,000 8 16,941,000 1954 49,772,000 14,119,000 1955 55,062,000 11,417,000 1956 7 55,696,000 9,706,000 1957 49,915,000 6,055,000 1958 49,246,000 5,661,000 1959 58,246,000 5,596,000 _ 5 _ The substantial drop in gross income from eggs over this period (1955—1959) is evident, but on a percentage basis, there was a greater decline in the gross income derived from the sale of chickens. This decline in the gross in- come from the salvage hens has been considered by some poultrymen when decisions were made to carry over the old hens into an extended laying period. Poultry are no longer kept on seventy (70) percent of the farms in the State of Michigan. rAccording to the Census of Agriculture (1954), only 86,214 farms out of the 158,945 farms reporting-had flocks of laying chickens (62%). Of the 86,214 farms, 62,164 were commercial farmsl having laying hens; and 24,050 non-commercial farms were reported as having laying hens. 0f the number of commer- cial farms having laying hens, 52,255 farms report flocks containing less than 100 birds (Figure 1). There are a number of large "commercial" flocks (1,451 farms) with 800 or more layers per flock. .Thus, flocks of chickens are becoming fewer but larger, and the industry, as a whole, is becoming more intensified. The 52,255 commercial farms having less than 100 layers per farm sold 5,048,000 dozen eggs in 1954. Whereas, the 1,451 farms having 800 or more layers reported the sale of 17,976,000 dozen eggs. Farm flocks (on 28,478 farms) consisting of 100 to-800 hens 1Census of Agriculture (1954), $1,200 or more in— come from farming. Percent 100”. , 90--» 80---- 70.x Hare l Percent 100 — -.—~1n——~—-.-[~— 7-r..ln__-llll.l._Tfni ,i___ l__n_1 4 \l 90 - —*—~* h\“~<;-\:\\\N —w~wwf~* ’— 7o--n c. 1.11.11“ 1 w ’1 60 - -.“ul .fi_~_- 7 - ~H——— — 4——»_-H 1 l 1 l F l . A 4 50--»——- r e i l 4 40-- l l .-___1 1 O_$ A L J 1920 1950 1940 1950 1954 Year Figure 1. Percentage of Total Michigan Farms Reportin Chickens, (1954 U. S. Census of Agriculture . produced 46,012,000 dozen eggs for sale during this same year. Today, a smaller percentage of Michigan farmers keep layers than 25 years ago. ‘However, those farmers who have continued the poultry enterprise keep larger flocks and thereby, produce more eggs than they did during the earlier years (Figure 2). The increased egg production per farm has been the result not only of larger flocks but also has been due to an increased annual egg production per layer. The increased egg production per layer has been due to improved breeding, improved control over environ- mental conditions especially housing, improved management and feeding practices coupled with improvements in rations fed. According to the 1954 Census of Agriculture, during the 25 year period of 1925-29 to 1950-54, the average egg production per layer in the United States increased from 95 eggs per laying hen to 148 eggs per layer. This is a 60 percent increase. In Michigan, during the period of 1925-29, the average egg production per hen was 98 eggs per year, whereas, in 1950-54, the average annual egg pro- duction per layer was 155 eggs, an increase of 56 percent. The 1959 Census of Agriculture data showed that in 1958, the average annual egg production per layer in Michigan was 202 eggs, while the national average was 201 eggs per layer (Figure 5). 17 16 H H m \N l-' H |-‘ O O‘VICDKO \J'I Egg Production in Thousands of Eggs 1925 1950 1955 1940 1945 Figure 2. Year Egg Production per Farm, Michigan, 1925 - 1950, (Agricultural Marketing Service, U.S.D.A. . .f . s p _ / h 8U 0 AL. 9v AU 0 l w m/. 0 n3 ,0 [4. A C MW «5 s C at l ... . .54 l l {A . .4 .UKAJU‘H .4 «U hi mh~r¥wnfi be 10 220 200 180 / l—‘ 0" O \ H n O Eggs per Layer / 120 100 f 1925 50 55 4o 45 5o ' .‘55 60 Year Figure 5. Eggs Laid per Average Michigan Layer Kept Dur- ing Selected Years, 1925— 59. 1 Agricultural Marketing Service, 1961 Outlook Issue, Pbultry and Egg Situation, U. S. D.A. I U 5" V. .1 v... .2 .7 “a “a n1 . I / \I/ 31‘ 0v «1 L. :1. ..:J . ~. rm "v.4 ~ . ~3 .- .1. :1 2 a: .. ‘ l . 1W \——" o $3197" ‘ “‘55.. ul» Q ‘4 9c .... ‘V Q.— AO‘FK , . VI a}, “U - V .11 Seasonal Variation in Egg Production and Pricgg During the past 25 years, the seasonal egg produc— tion curve of the Midwest has gradually leveled (Mortenson, 1956; Figures 4 and 5). Over a period of 5 years, (1950- 54), peak egg production during the months of March, April and May averaged only about 20 percent above the seasonal average; whereas about 25 years earlier, this percentage figure ranged up to 65 percent. Likewise the low point of production, in the fall of the year, did not drop nearly as much as it did 25 years earlier. The leveling of the egg production curve has also had the effect of leveling the seasonal variation in egg prices. During 1925-29, egg prices peaked at 60 percent above the annual average as compared with 15 percent above the annual average egg price during 1950-54. Egg prices dropped 20 percent under the annual average egg price dur— ing the years of 1950-54; during the years 1925-29, the seasonal variation in egg price was 58 percent under the average annual egg price. Mortenson (1956) observed that egg producers in some areas of the United States experi- enced a more pronounced leveling out of egg prices than did Midwest poultrymen. These poultrymen not only had larger flocks but also kept them longer. This researcher further noted that in other areas the poultry flock was the secondary farm enterprise and that no real attempt was made to maintain uniform egg production throughout the Perc‘ 130 160 140 123 130 t. 40 P- alms 4. {Orté 12 Percent 180 160 / / / 140 // x \ ,1’ \ / 120 . r I \\ \ / \, r/ \ ,i 100 \ / \ , // \\ ’_ , , ’ 8O \ \ ’ a— " 4O -——— N. U. Region g ProductLon \\——" -_._1_. U. S. Egg Price (AvFrage Farm Price) 20 F M A M J J A S Month Figure 4. Monthly Egg Production and Egg Pricei for the North Central Region in 1925 - 1929. Mortenson (1956). Perce 140 120 130 1 / '2! I’ié’ure 5. Home 13 Percent N. C. R gion Egg Production —---—n—-Average U. S. Farm Egg Price 140 /\ 120 / // ,—-~'”"‘ \ // h\‘__——\‘\\q~ L’/ 80 k/// 60 40 20 J F M A M J J A S 0 b D Month North Central Region in 1950 - 1954. “— lMortenson (1956). Figure 5. Monthly Egg Production and Egg Pricei for the flue bhe NH». ‘ VAA ,e v arac p1- VA. 1 Partic Mn \a I 'I x “3 14 various seasons of the year. Economically, the leveling of egg prices should in- I fluence the plans of a poultryman with respect to filling the laying house, if seasonal price advantages do not exist. Further economic consideration which may affect the management plans of an egg producer would be the factor of seasonal differences in total egg production. Addi- tional questions which should be answered include: (1) Are there significant differences in seasonal egg prices when considering egg size? and (2) Are there different seasonal patterns of egg size in the total production curve? 'Total Egg Production The relative importance of the various production characteristics which determine the profitability of a particular strain of chickens is of great concern to com- mercial breeders of egg—type chickens. As early as 1918, Goodale pointed out that hens tended to have a characteristic rhythm of egg production which, however, was obscured by irregularities and seasonal effects. Recently, Nordskog (1960) reported that correla- tions existed between the performance factors of egg size, body size, mortality and rate of egg production. There- fore, it may logically be expected that a strain superior for one characteristic would tend to be superior or talit; ferezc Actual 1; , 01‘. IS 0f eg: 15 inferior for another characteristic depending upon the direction of the correlations between the traits, i.e., positive or negative. Nordskog (1960) also found, upon analyzing the data from 21 separate random sample tests which involved Leghorn—type entries, that the expected value of a 10 egg increase in production would be worth a net Value of 51.5 cents and a 10 percent increase in egg size would be worth about 19.2 cents. He further observed that two factors--the rate of egg production and the mor- tality rate--accounted for the major portion of the dif- ferences observed between the entries in net income. Actually, the results obtained from each of the test loca— tions showed a remarkable consistency except for the trait of egg size. Seasonal Effects . Abplanalp (1957) used fixed period measures of pro- duction and concluded that there was little to gain from considering hatch effects in the selection of breeders. Bray, King and Anderson (1960) noted that hatch effects must be considered as a possible source of variation if egg production data were to be efficiently analyzed and utilized. Sexual Maturity Oliver gt g1. (1957) reported that annual percent- age egg production is little affected by age at sexual .l \/ At Au .ou r: o. Y. (A n» Y. C .wA v. »« ‘1‘ 2. TA . . r d .,c r“ .. . r n: i. a: + v J‘u .. c 1. 4 :0 A: Q. it Hi Y. A... nu [my «A; uh “L fly .HM V“ ~u. ‘5“ a: .\|# 9 ‘ e h“ M .k . J.‘ N.‘ +v an. . at A0 to ac .~ u r “1 u ~ 3. n y by a. . Z .3 w. s. .n a a ll :1 r us .3 r. mu ‘9 av AV 1 n1 0 .s a : a .x . . a a a» x. O. m a. 1 .9. V1. 69 a .7. a 01 :1 a. . L .. . A a .5 m .. n. . s A u h. . It. s u at I! 16 maturity. However, the more recent work of Bray g3 g1. (1960) demonstrated that sexual maturity played a signi- ficant role in estimates of heritability when egg numbers from data of first egg was the measure. Nutrition Kurnick gt g1. (1960) varied the caloric content of the ration fed to Single Comb White Leghorn laying hens and studied the effect of season of hatch on their per- formance. The pullets were hatched so that they matured at definite intervals throughout the year. When the data for total egg production were analyzed, these researchers found that the production was exactly the same over the ll-month laying period for the females fed three diets, each of which varied in caloric content. Location Influences It is generally recognized that in order to make ef- ficient performance Comparisons between laying chickens of different breeding, it is important to know how sample size, testing location, and year of test influence the fre- quently observed differences in egg production. A question of special significance in any testing program is that which pertains to the importance of gene- tic X environmental interactions. For example, will a strain of laying chickens that is superior for total egg production during one year at a certain location be 1? superior at other locations and during other years? The importance of obtaining a correct answer to this question is becoming increasingly recognized, as more and more stu- dies are being undertaken to determine the effects of genetic X environmental interactions on egg production. Munro (1956) recognized the possibility that gene— tic X environmental interaction might seriously hamper progress in breeding for improvement in egg production. However, in the egg production studies of Gutteridge and O'Neil (1942), no significant interaction between genotype X location was found. These researchers also studied the age at sexual maturity and the egg weight of three differ- ent strains of Barred Plymouth Rocks tested at three widely scattered locations. They found that no significant interaction existed between genotype X location. Gowe and Wakely (1954) stated, " . . . the practice of comparing the genetic worth of strains of fowl on test at different locations is of little value or no value." However, Hill and Nordskog (1956) stated that the "Test- ing of varieties in five locations and retesting of the selected varieties for one or two more years . . ." was "a practical procedure for evaluating strains or hybrid Varieties." Related to the location effects would be the con- sideration of pen effects. From a study of laying experi— ments on the semi-intensive plant at the Agricultural 18 Research Institute of Northern Ireland, Hale (1952) con- cluded that egg production was seldom affected by differ- ences between pens that were treated alike. Hale (1959) continued the 1952 study and reported that no significant pen effects were evident. He also noted that hatch effect was significant in only one year. Egg Size Distribution Season The relationship between egg weight and annual egg production has been studied by many investigators, and the seasonal influence on egg size has been well demonstrated. Harris and Goodale (1922) reported that egg produc- tion during the fall, winter, or late summer was a better measure of total egg production than was the measure of egg numbers laid during the spring months. Conflicting information exists in the literature concerning the relationship between average annual egg weight and total egg production. Parkhurst (1926) reported that there was no correlation between the egg production record for 565 days and the average egg weight during the entire year. Marble (1950) observed that the correlation between egg weight and annual egg production was signifi- cantly skewed and that the regression of egg weight upon annual egg production was significantly non—linear. The hens which were kept for an extended period of lay (the SGCO Witt 0‘“ - . . C 19 second laying year) also showed a significant non—linearity of egg weight and annual egg production. Further studies by Marble (1951) involved the interrelationships of body weight, high egg production, early sexual maturity and the selection of certain size eggs for setting on the average annual egg weight. He concluded that there are numerous other undetermined factors which influence egg weight, other than those factors studied. On the other hand, Blyth (1952) concluded that egg weight was negatively associated with a basic maximum rate of egg production. However, this relationship did not hold true for the poorer producers because irregularities in their egg production performance constituted divergen- cies from their maximum potential. Poultrymen have long noted that for spring hatched pullets, egg weights usually increased from October to February or March, and that a gradual decline in egg weight occurs during the summer months. The foregoing ob- servation was substantiated by Jull (1924) who found that egg weight increased from December to February and de- creased from February to April and by Funk and Kempster (1954) who observed that the largest eggs were produced during the months of February and March. The effect of season of the year and the age of the bird on egg size, egg quality and total numbers of eggs laid by hens of different ages was investigated by 2O Cunningham 23 gl. (1960). These researchers found upon analyzing data obtained from layers kept under widely dif- fering environmental conditions that the different environ- mental conditions did not affect seasonal differences of egg size distribution. The magnitude of the seasonal dif— ferences in egg size distribution was less than that which resulted from the effect of aging upon the bird. Agg It is generally rec0gnized that females lay larger size eggs during their second year of egg production. Clark (1940) noted that a significant increase occurs in the average egg weight during the second laying year. Jeffery (1941) suggested that egg weight was the result of the interaction of body weight, environmental temperature, and age. Sexual Maturity Tonaka and Rosenberg (1952) generalized that if a pullet matured too early in life that the initial egg size would be smaller than the egg size of pullets which ma— tured later. On the other hand, they suggested that an early maturing pullet may lay for a longer period and con- sequently would produce a greater number of eggs. They also observed that "short-time" egg production records made during certain seasons of the year may be useful in predicting total annual egg production. 21 Temperature It has been postulated that high environmental tem- peratures reduce egg weight. Temperatures were not re- corded for the different seasons of the year by Bennion and Warren (1955) and Warren and Schnepel (1940) when the influence of temperature on egg size was investigated. Warren gt Q1. (1950) reported that the egg weight increased during the laying year if the birds did not encounter high summer temperatures. In Hawaii, Rosenberg and Tonaka (1951), working with New Hampshire pullets subjected to a maximum average temperature of 80° Fahrenheit, observed that egg size increased continually for the first 11 months of lay. I The influence of high temperatures on egg weight was also investigated by Hutchinson (1955), but no practi- cal means of recording laying house temperatures was pro- vided and therefore no seasonal effects were noted. Egg Quality Studies The availability of improved strains of laying hens in recent years has resulted in an increasing number of poultrymen who consider keeping layers for a second year of egg production. While adequate information is avail- able on the changes in egg quality which occur during the pullet year, only limited experimental evidence is avail- able on the effect of the age of the bird on egg quality duri 22 during the second year of egg production. As a general rule, the relative amount of thick al- bumen decreases with the length of time that the bird has been in production. Hunter 23 gl. (1956) and Lorenz and Almquist (1956) studied the albumen quality of the eggs laid by birds during their pullet year and found that a continuous decline in albumen quality occurred from the spring months to the fall months. Warren g3 g1. (1950) also reported a definite decrease in albumen quality as the pullet laying season prOgressed. They noted that a drOp occurred in the albumen quality of the eggs produced by females housed in both controlled and uncontrolled en- vironments. These researchers concluded that the drOp in albumen quality was due to factors inherent in the bird and not due to external environmental factors. Sauter g3 g1. (1954) investigated the effect of both age and season on egg quality and found that the eggs laid during the winter months were of a higher albumen quality than eggs laid dur- ing the summer months. Grotts (1956) reported that a general decline oc— curred in Haugh units in the eggs produced by both floor and cage layers throughout the year. Froning and Funk (1958) also reported that seasonal variations existed in the Haugh units of the eggs laid by both floor and cage layers. Lamoureux (1957) analyzed the data from the Seventh California Official Random Sample Egg Laying Test 25 pertaining to the average decline in Haugh units of eggs laid by March and April hatched birds. He found that the average decline in Haugh units during December to August was 15.5 units for the crossbreds and 10.4 units for the light breeds. Strain and Johnson (1957) found significant hatch and strain differences during the month of October in the traits of egg weight, shell strength, and albumen quality. However, the hatch differences were maintained for egg weight and albumen quality throughout the year. Measurement Dawson and Hall (1954) found that the greatest de- cline in albumen quality occurred during the first three days after the egg has been laid, regardless of the hold— ing temperature. Temperatures of 60° Fahrenheit or lower were found to be practical for normal farm holding of eggs. Spencer 33 gl. (1956) observed that the albumen quality declined linearly with the logarithm of elapsed time from break-out. They also reported that individual hen varia- tion and the age of the egg influenced the rate of loss of egg quality. Fry and Newell (1957) observed that the ini- tial drop in egg quality was the greatest. They also found that at holding temperatures of 50°, 60°, and 90° Fahrenheit, the decrease in Haugh units for the first 48 hours of storage was significantly greater than the decrease for any succeeding 48-hour period. 24 Strain Dawson 93 gl. (1955), Cotterill and Winter (1954), King and Hall (1955), and Johnson and Gowe (1956) found that the initial interior quality of fresh shell eggs varied between and among different breeds and strains of chickens. May gt gl. (1957) confirmed the findings of the above workers and in addition, these researchers found the rapidity of decline of albumen quality also varied between and among the different breeds and strains of chickens. Age of Birds Jull (1955) found that interior egg quality declined as layers increased in age. Cunningham 23 gl. (1960) found that the decline in Haugh units of eggs was due entirely to the aging of the bird. Seasonal changes did not in- fluence the initial interior quality of eggs in this inves— tigation. Mueller 23 gl. (1960) noted that the lower Haugh scores observed during the second year of egg production were probably due to the effect of age of the bird. The variability observed in the Haugh unit scores during the second year of production was considerably higher than the variability during the pullet year. On the other hand, Snyder and Orr (1960), in a study of commercial poultry farms, found that length of lay did not affect the rate of decline in egg quality. In this latter study, the interior quality of the eggs laid by the oldest group of females 25 was found to be lower by approximately 10 to 15 Haugh units than those of the youngest group of females. In addition, the interior quality of the eggs from the older hens showed a greater variability. Blood Spots Meat and blood spots have long been recognized as a serious problem by poultrymen Specializing in the produc- tion of table eggs. The literature on this subject is voluminous. One of the earlier reports was by Jeffery and Pino (1945) who suggested that heredity was an important causative factor in the production of blood spots in eggs. To date, only limited experimental evidence is available on specific environmental factors which influence the incidence of blood and meat spots in eggs. The effect of season of the year on the incidence of these inclusions in eggs has been studied by Sauter 23 gl. (1952) and Johnson (1956). Sauter gp g1. (1952) found that there was a definite and statistically significant seasonal variation in the incidence of blood spots. These workers observed that the percentages of total eggs having blood spots were lowest in December. Johnson (1956) observed a distinct seasonal trend in the incidence of blood spots increasing gradually from November to June. accezt< shell 1 319.1: 5;". L . ell: 3'") 26 Shell Thickness Romanoff and Romanoff (1949) cite that shell thick- ness decreases from March to September of the pullet year. They noted that the variation in egg shell thickness dur- ing the second year of egg production, or over an extended period of lay, has not been investigated. Warren and Schnepel (1940) demonstrated that hens subjected to high environmental temperatures (90° Fahren- heit) had a thinner egg shell than normal. High humidity accented the depressing effects of high temperatures on shell thickness. It was observed by Mueller 23 Q1. (1960) that shell thickness during the second year of egg produc- tion was significantly (5% level) higher than shell thick- ness during the pullet year. These researchers suggested that the differences in shell thickness between the first and second year of egg production were caused by environ- mental factors and not by the increase in age of the chickens. Pfost (1960) noted that the change in shell thickness appeared to be a straight line decrease with age of the bird. According to this investigator, there seems to be a seasonal effect on shell thickness but no seasonal effect on albumen height. Correlation of Hatch Date, Annual Egg Productiog_and Egg Size Distribution The literature dealing with the relationship of to- tal egg production, egg size distribution, egg quality L:A U.v L. If: C012 the e a stud; 'ate. @1311, 51011 t tern, a. 27 changes and seasonal egg price patterns is rather limited. The poultry farmer should be interested in such correla— tions, especially in view of a reliable expected egg price pattern. McKee and Gervais (1958) reported that seasonal rearing of replacement pullets in four separate hatches and keeping the laying birds to 22 months of age was the most profitable management system. These investigators stated that late summer and early winter months of pullet rearing coincide best with favorable egg prices later. Kinder and Funk (1960) reported that seasonal effect of hatch date on production performance was marked and that the effect of hatch date on seasonal egg size pattern was even more pronounced. These workers utilized a three—year study with February, June, and September being the hatch dates. They found that February and June hatch dates were the most profitable. These researchers concluded that the date of hatch definitely affects the length of time that egg-strain layers should be kept for profitable egg produc- tion. 0n the other hand, Platt (1960) reached the conclu- sion that satisfactory results could be expected in egg production despite the season of hatch. He noted that it would seem desirable for the poultryman to operate in ac- cordance with his own convenience rather than on a set pat- tern, as over a series of years the hatching date may not be of particular economic importance. ‘ A,“ p’ irate—lus— Ih’ )hv,.~‘ ‘Lu:;‘ ll» ‘ ... . «Hy, + MATERIALS AND METHODS Description of thg Poultry Farm Used in This Study The commercial poultry farm organization known as the Harry Burns Poultry Farm, Inc., of Millington, Michigan, was the site for the investigation reported herein. Since approximately 20,000 laying hens are kept on a year-round basis on this poultry farm, it is necessary for the manage- ment to brood chicks at various times of the year. Care- ful planning is therefore necessary to keep the laying pens full at all times if the management is to operate at peak efficiency. The corporation's market for shell eggs (produced exclusively by the corporation flock) consists of retail sales at the Detroit Eastern Market and also the wholesale outlets of an egg-buying station and a retail store. All eggs produced on the poultry farm are processed by em- ployees of the corporation. Strains of Chickgns Used The commercial strains of laying hens used in this investigation were "H & N" (Heisdorf and Nelson) and "Hylines." The strains used and years of tests were as follows: _ 28 _ V A an 4 ‘ n: z. n. I. no .3 6. TD "a .1 a .3 . I a . a a a o .. . D» a. .2 ..u v« .1 u.. .1 .2 to .nu 7s . . :n C .. . e. . g 29 Strain Code Commercial Name Egg; I H & N 1958 II Hyline 1958 III H & N 1959 Iv Hyline 1959 It is recognized that although the commercial de- signation of a stock may remain the same over a period of several years, one does not have any assurance that the breeding procedures used by the breeder are the same from year to year or within years. Therefore, it is possible that the H & N stock of 1958 may differ greatly from the H & N stock of 1959. This could also be true of the Hyline stock. In order to study the effects of seasonal hatching on certain egg production traits, the annual hatching dates selected for purposes of this study were six differ- ent months of the year. The different months are desig- nated herein as "hatching seasons" and were as follows: Hatching Season Approximate Date of Hatch February 1, 1958 April 1, 1958 June 1, 1958 August 1, 1958 October 1, 1958 mmuow» December 1, 1958 .L . TA :1 ... r. a. kn nb_ 11 .2 a A a fit .. . Cu C ANV may 0/ AV! a. «1 aa .«a «1.4 va .. I I} C/ 3/ S . :1. a. z n. a We 2. L 01 flux nu/ Au} 5 n. n. ‘2 ha wv. VJ. l ‘1‘ l 1:» 1‘? o 338d L A the I :5 00 50 These dates were selected not only to fit into the commer- cial poultry farm operation but also to be representative of a range of hatching dates over a period of one year. Brooding and Rearing Procedures The day—old chicks used in this experiment were brooded, using radiant heat and supplemental hot water radiators, at intervals of approximately two months in a house used exclusively for this purpose. The dates of hatch and the brooding schedule were as follows: FxH'Strahi Season, Month, and Day of Hatch A B C D E wwwmwmmmwmmm 1958 I 22 4 4 6 27 5 1958 II 4 6 5 1959 III 4 1 6 5 1959 IV 4 1 During the brooding period, the intensity of light was limited to prevent cannibalism. The pullets were reared from six weeks of age to approximately 18 weeks of age in a separate rearing house. Hence, the females were reared in confinement. No special lighting program (such as H & N Controlled Lighting Program) was used during any of the rearing periods. During all phases of the brooding and rearing periods, and during the egg production periods, strict 51 sanitation procedures were followed. Unauthorized per- sonnel were not allowed in the brooder house or in the rearing house. The chicks of all hatches were vaccinated for Infectious Bronchitis and Newcastle Disease. The vac- cines used were of the water type. No Fowl Pox or Laryn- gotracheitis vaccines were used. Numbers of Females Housgg In the investigation reported herewith, the term "extended lay" is interpreted to mean that the laying fe- males were retained for a period of time longer than is practiced in commercial egg production enterprises. The numbers of pullets housed each season (month of hatch) by years and the numbers of females kept for the "extended lay" test period were as follows: Season of Hatch Year Strain A B C D E F (Number of Birds) 1958 I 2000 1560 2592 1250 2400 750 1958 II 590 1210 750 1959 III 600 1204 2594 2527 1959 IV 1215 1204 "mended Lay" l 1 l l l l 1958 Hatch 405 1172 500 500 1057 750 1Numbers of Strain I females used for extended lay study. sent: far 1 were ans 2 recor used Weeks 52 From the foregoing, it can readily be seen that only a representative sample of the laying hens of Strain I were kept for the extended lay study. However, the hens which were.used in all extended lay analyses were repre— sentative of the various hatching seasons. The hens used for the extended lay test period were retained until they were 50 months of age. The term "period" in this study indicates the vari- ous 2-week periods (14 days) that the egg production records were kept. The term "period" therefore can be used to indicate the approximate age of the females in weeks by multiplying the "period" figure by two. Environmental Conditions Kgntilation and ngpgrature Control Annual temperatures in the laying houses or pens were within the range which are generally encountered under typical Michigan conditions. The laying houses were equipped with a mechanical ventilating system for the re- moval of moisture and for temperature control. Thermo- statically—controlled ventilating fans were located on the lee side of the poultry houses. Essentially, the air was drawn in through attic louvers and pulled down into the laying pens by the fans. The ventilating air was drawn across the laying pens. Some pens were equipped with direct vents to the outside air, however. 0 .H/ [It 533?; n. P . u-rs .. t. v u v 55 The thermostatic controls of the fans were set at 55° Fahrenheit. Auxilliary heat, from steam heat radia- tors, was provided during the colder months. The thermo- static controls for auxilliary heat were set at 50° Fahrenheit. The average monthly outside temperatures recorded for the nearby area of Flint, Michigan, are shown in the Appendix (Table 8). Farm records indicated that the out- side temperature closely approximated 0° Fahrenheit from February 8 to 21, 1958. The farm records also indicated a -10° Fahrenheit temperature on January 6 and on February 10, 1958. Lighting Procedures The laying hens were given a l4-hour light-day. A 60 watt incandescent bulb was used for each 200 square feet of floor space. Light meters were used at periodic inter- vals to assure that the laying hens were receiving at least one foot-candle of light at the eye level of the bird. The lights were turned on at 4:00 A.M. during the periods when additional light was needed to provide a 14- hour day. Evening lights were not used and the layers went to roost by natural daylight. l . . \ L _ - 1 CC 6 ..,: . :. ~. I Ce 1 . L A. UL no a C “a nu G» .~$ r1. 3. a: w A A: .1 VI r.. y: ND e e r .. 1 w _ an e at 11 . v e a «U .C a l k, u A: 1“ vv «Irv ~m e w‘v «D .1 Wm n . nu rd 9 in ya u cl .. 2 .1 .6 AV ~11 a .1 u G; a. .VL Ly .w .. z n1 .1 T: : < ll at P )1 V1 c h. rn {A . a b o _ A 3; A: av AIL. H. ' . «c.1126 54 Nutrition The laying females were fed a 17 percent protein laying mash. This laying mash was made from a 42 percent commercial concentrate mixed with home-grown corn. Sup- plemental whey 50-pound blocks were provided for the layers. Miscellaneous Envirogggptal Factors Except for the removal of obviously sick birds, culling of the laying flock was not practiced. All females removed for health reasons were recorded as death losses. All pens of birds kept for all extended lay periods were kept intact. To avoid placing any possible undue financial hardship on the corporation, a deficiency pay- ment agreement was drawn up between the corporation and the Poultry Science Department and the Agricultural Econ— omics Department of Michigan State University (Appendix Table 1). During the period of this study, the eggs were gathered in wire baskets and washed on the same day. The eggs were graded and sized on the following day. Commer- cial egg processing equipment, known as Eggomatic, was used. This equipment included a flash candler, a sanding machine, and a sizing machine. The eggs were cartoned and then refrigerated in a walk-in cooler which was operated at a temperature of 55° Fahrenheit and a relative humidity ..“ UAV- ~~ 'Lna VNO «a , .. -gt n‘ " h e. I“ a“ \ ‘».,, ~ 4:4. MVIVV 17.... Mr M.“ & n . “53:“; ' ~ 55 75 percent. The egg processing room was air conditioned and/or heated to a constant 70° Fahrenheit temperature throughout the year. Characteristics Mgasured The total egg production, seasonal egg size distri- bution, and selected egg quality factors were measured for the females which were hatched at different seasons of the year and retained for the extended lay test period. Complete data for total egg production were avail— able for analyses of all strains of laying hens used. How- ever, only representative pens of layers of the various strains were selected for analyses of seasonal egg size distribution. The egg size distributions, expressed in total num— bers of dozens of eggs produced by the different strains of layers, were calculated from the egg production data. As stated previously, seasonal changes in selected egg quality factors, as affected by hatching date, were investigated. The egg quality factors measured were al- bumen quality, shell thickness and blood spot incidence. In summary, data were collected and analyzed, wherever possible, for the following traits: 1. Total egg production. 2. Egg size distribution. 5. Egg quality factors. 56 4. Feed consumption. 5. Mortality. The record-keeping forms that were used in this study are shown in the Appendix, Tables 2-6, inclusive. Total Egg Production Poultrymen are well aware that there are many dif- ferent ways of expressing total egg production, e.g., hen-dayl percent production, hen—housed2 egg production, and survivor's production. In this study, daily egg pro- duction records were kept to determine the effect of hatch— ing date on total egg production, and the statistical analyses are based upon hen-day production calculations. However, the analyses of numbers of dozens of eggs of the various size classifications are based upon numbers of females housed, i.e., hen—housed data. Jerome, Henderson and King (1956) and Oliver, Bohren and Anderson (1957) suggested that mortality in the . laying house "clouds" the exact measurement of egg pro- duction. For purposes of statistical analyses (and for selection programs) Bray, King and Anderson (1960) suggested 1 Total egg production for . 2-wegk period Hen-day egg production = Average number of females in pen during 2—week period 2 Total number of eggs Hen-housed egg production = __guring the year Number of females housed .l.| . 57 that the non-producing hens be removed prior to making calculations of total egg production. Therefore, these researchers use hen-day production. On the other hand, the practical commercial poultryman is vitally interested in hen-housed egg production. Egg Size1 Distribution Egg size distribution data were kept on selected pens of layers. These data, expressed as percentages of , total egg production, were collected on two consecutive days every two weeks. Egg Quality Factors Considerable research evidence is available in the literature on egg quality changes during the pullet year. However, experimental evidence of the effect of age on egg quality during the second year of egg production is, with the exception of egg size, relatively limited. Therefore, in this investigation, egg quality changes during the ex- tended lay period were studied and are reported. Records were kept on egg weight, albumen height, shell thickness and blood spot incidence for the extended lay females. Every two weeks during the extended lay lEgg sizes are designated as weight in ounces per dozen: "Jumbo" - 50 oz. and over; "Extra-large" — 27 oz. to 50 oz.; "Large" — 24 oz. to 27 oz.; "Medium" - 21 oz. to 24 oz.; "Small" - 18 oz. to 21 oz.; and "Peewee" — 15 oz. per dozen eggs. 58 period, a random sample of two dozen eggs from the layers hatched at different seasons of the year were collected for egg quality measurements. The numbers of sized eggs (e.g. jumbos, extra-large, large and mediums) collected for quality measurements were drawn in proportion to the total number of dozens of eggs in each size classification. The final quality measurements of the egg samples were made in the Poultry Science Department at Michigan State University. The procedure used for measuring inter- ior egg quality was that of Brant and Shrader (1952). Cur- rently, this method is in widespread use in egg quality research laboratories and is used in egg laying tests. The egg weight, recorded to the nearest gram, was determined by the use of a Toledo balance. Each egg was broken-out on a level glass plate, which was supported by a metal stand. The albumen height was measured with a tripod micrometer. The albumen height and weight measure- ment were used to compute Haugh units as a measure of in- terior egg quality. (Haugh, 1957). The Interior Quality Calculator for eggs (American Instrument Company, Inc.) was used for the Haugh unit computations. Shell thickness was determined by a thickness gauge calibrated in thousandths of an inch and both shell mem- branes were included in the measurement. All measurements were taken while the shell and the membranes were wet. 7'“ .1. AA“ e..- 11 .3. Va“ 59 The incidence of blood spots was noted at the time of albumen height measurement. The inclusion size, color and location on the broken-out egg was observed by means of eye with aid of mirrors located under and behind the glass plate which was used for measuring the albumen height. It should be noted that the observations of the inclusions were made after the eggs had passed over the commercial flash candler. For each two-dozen sample of eggs which were broken-out, the number of inclusions are recorded in actual figures. Therefore, although the egg graders (employees) had attempted to remove the obvious blood spots (which were recorded as percent blood spots at that time), they did fail to remove any pinpoint blood spots. The observations of each two-dozen egg sample was then, in reality, a record of the pinpoint blood spots not readily detectable by the process of flash candling. The eggs with blood spots removed by the candler were recorded, and in addition, the cracked and checked eggs (undergrades) were included in the egg size distribu— tion data. The Relationship of Total Egg Production to Egg Size Dis— tribution In this study, the total number of eggs laid by the females hatched at different seasons of the year and kept for the extended lay period was tabulated according to egg size renal 6 r a. S tical 3531‘s bet-Eff 1941) 40 size distribution. These data were converted to a 1000 female basis to facilitate and equalize computations for the strains of layers tested. These data are presented as cumulative monthly totals. Statistical Procedures Employed The four strains of commercial egg-type females used in this investigation are hereinafter referred to as Strains I, II, III and IV. As previously stated, the fe— males were hatched in February, April, June, August, Octo— ber and December. Again, these hatching dates are referred to as Seasons A, B, C, D, E, and F, respectively. All possible comparison combinations were statis- tically analyzed with strains, by hatching dates and within years. Further, comparisons were made between strains and between years where similar hatching dates were involved. All data were subjected to an analysis of Variance (Snedecor, 1944) and Duncan's Multiple Range Test (1955). RESULTS The data in this thesis are presented by individual hatching-season comparisons within years and within and between strains of laying hens. The hatching-season com- parisons, i.e., hatching-season A versus hatching season B, are discussed in the following order: Strain I Comparisons A vs. B B vs. C C vs. D D vs. E E vs. F A vs. C B vs. D C vs. E D vs. F A vs. D B vs. E C vs. F A vs. E B vs. F A vs. F Strain II Comparisong B vs. D D vs. F B vs. F Strain III Comparisons A vs. B B vs. C C vs. D A vs. C B vs. D A vs. D Strain IV Comparisons A vs. B Due to the cross-references necessary when indi- vidual hatching-season comparisons by strains are made, the Tables and Figures are included in one position in the thesis. These Tables and Figures are presented in pages 99 to 169, inclusive, in the order of the data outlined below. _ 41 - 42 Within the individual hatching-season comparisons, the following data are presented where information was available: 1. Total egg production. 2. Pen differences in total egg production. 5 Statistical analyses of total egg production. 4. Egg size distribution. 5. Haugh unit scores of eggs laid during extended lay periods. 6 Shell thickness of eggs laid during extended lay periods. 7. Blood spot incidence. 8. Dozens of eggs produced. Strain I Comparisons Eggson A (February hatch) versus Season B (April hatch) The average numbers of eggs laid by the females hatched in Season A and B are presented in Table l, and the average numbers of eggs per two-week period over the 54 bi-weekly periods are graphically plotted and shown in Figures 6 and 7. It should be noted that the egg produc- tion records began with bi-weekly Period 12, when the fe- males were 24 weeks of age and when the egg production records were available for the females hatched in all six seaSons of the year. Prior to Period 12, complete data were not available for all hatches of Strain I. It is important to note that the females which were hatched in Season A were housed in one pen, whereas the females which were hatched in Season B were housed in three different buildings on three different farms. Therefore, 45 since pen X location interactions have been shown to exist, the logical step was to determine whether any differences existed between pens and locations for Season B hatched pullets. The analysis of variance of the egg production data showed that no significant differences existed between pens at different locations, (Tables 15, 14 and 15). Thus, the egg production data for Season B hatched females were pooled for comparison purposes. The females hatched in February laid at the rate of 4.9 eggs per bird during Period 12. Whereas the females hatched in April laid at the rate of 1.9 eggs per bird for the comparable period. This higher production trend con— tinued throughout the 54 two-week periods and was reflected in the production means of the two hatches (February, 9.27 eggs per bird per two-week period; April, 7.47 eggs per bird per two-week period). The mean differences of 1.80 eggs per bird per two-week period in favor of the February hatched females was highly significant (P «0.01, Tables 5 and 6). It will be noted in Table 1 that the February- hatched females reached a peak egg production of 11.9 eggs per bird per two-week period at 52 weeks of age; whereas the April-hatched pullets peaked at 10.6 eggs per bird at 54 weeks of age. Further, the February—hatched pullets maintained a rate of egg production of over 10 eggs per 44 bird per two-week period for 28 consecutive weeks while the April-hatched females laid at this rate for only eight weeks. The egg size distribution in percentages for the February and April-hatched females are presented in Tables 28-54, inclusive. The egg size distribution data are graphically presented in Figures 15 through 20. Figures 15-18,inc1usive, show the percentages of comparable indi- vidual egg weights by hatching date per two—week period, whereas Figures 19 and 20 illustrate the complete egg weight distributions for the February and April hatching dates. The egg size distribution of the large, medium and small egg weight classes was affected by the season of produc- tion. The production of medium-sized eggs was especially affected, as represented by a substantial percentage in- crease, during the spring and summer months. Comparisons between the February and April hatching dates show that the February-hatched birds produced a higher percentage of jumbo, extra-large and large eggs than did the April-hatched birds. On the other hand, the April-hatched birds produced a higher percentage of small and peewee eggs than did the February-hatched birds. How- ever, there was no consistent advantage of one hatching date over another date in the numbers of medium-sized eggs produced by the birds. 45 Haugh unit scores of the eggs produced by the birds, in the extended laying period, are indicated in Tables 41 and 42. These tables are represented graphically in Figures 25 and 26. The Haugh unit scores of the eggs laid by the birds hatched in February were observed to be lower than the scores of the eggs laid by the April-hatched birds. The differences of Haugh unit scores between hatching dates were not consistent when comparable aged birds were plotted and shown in Figure 25. There was no marked season of production influence on Haugh unit scores between the hatching dates. Shell thickness data of the eggs laid by the Febru- ary and April-hatched hens are given in Tables 45 and 44. These data are graphically presented in Figures 27 and 28. There was no significant advantage of one hatching date over another hatching date in the egg shell thickness qual- ity factor. The shell thickness of the eggs laid by the birds hatched in February and in April declined slightly during the period of the test. The average shell thick- ness decline, measured in thousandths of an inch, was only 0.0005 of an inch. Detectable blood spot incidence data are presented in Tables 45, 46 and 47 for the eggs produced by females of the various seasons of hatch. Insignificant numbers of detectable blood spots occurred in the eggs produced by the hens representing both the February and the April 46 hatching dates. However, a greater number of blood spots were found in the eggs produced during the late summer, fall and early winter months. Females of both hatching dates were affected in a similar manner. No difference be- tween the two hatching dates (February and April) was noted in respect to the pinpoint blood spots observed in the broken-out eggs. Tables 49 and 50 indicate the cumulative dozens of eggs, by size, produced by hens hatched in February and in April. Table 48 gives the monthly egg production data in cumulative dozens of eggs produced. All data of the three tables are calculated per 1000 birds housed (hen-housed basis). The February-hatched birds produced a larger total number of eggs (8251 dozen) and larger number of eggs of the various egg weights (jumbo, 620 dozen; extra-large, 2870 dozen; large, 2480 dozen; medium, 1721 dozen; and small, 257 dozen) except for the production of the eggs of the peewee egg weight classification (101 dozen). Eggson A (February hatch) versus Sggson C (June hatch) The numbers of eggs laid by the birds of hatching Seasons A and C (February and June, respectively) are pre- sented in Table 1. The numbers in the tables represent the average numbers of eggs laid per bird per two-week period. The data are graphically plotted in Figures 6 and 8. These two hatches are compared on the same basis of the length of 47 lay and the period of lay. All of the batches of Strain I are compared in the same manner. It was noted in the discussion relative to the egg production of the birds of hatching Seasons A and B that the pen egg production data were pooled due to the non- significance of the differences in total egg production of the different pens. Pen differences in total egg produc- tion were highly significant from the birds of hatching Season C (Tables 16, 17 and 18). However, this pen dif- ference in total egg production was the only significant pen difference of the five hatches analyzed involving the divisions of similar strains into different pens. There- fore, the egg production data of these pens were pooled also. The females hatched in February laid at the rate of 4.9 eggs per bird during Period 12 in comparison with the rate of 1.0 egg per bird for the comparable period by the females hatched in June. As we pointed out in the earlier comparison, the February-hatched birds continued the high rate of production throughout the 54 two-week periods. In this comparison, the rate of lay per bird was higher for the February-hatched birds than for the June-hatched birds. The differences of the production means of the two hatches (9.27 eggs per bird for the February hatching season; 7.67 eggs per bird for the June hatching season) reflected this higher rate of lay of the February-hatched birds. The 48 difference of 1.6 eggs per bird per two-week period favor- ing the February-hatched females was highly significant. (P «0.01). Data from Table 1 indicated that the February- hatched birds peaked in egg production at 11.9 eggs per bird per two-week period, while the birds of the June hatching date peaked in egg production at 12.2 eggs. The June-hatched birds laid at a rate of 10 eggs per bird per two-week period for 12 consecutive weeks, while the February-hatched birds maintained the same production for 28 consecutive weeks. The data of the egg size distribution of the Febru-_ ary and June-hatched birds are presented in Tables 28 through 54. The complete egg size distributions of the total egg production by hatching dates are given in Tables 55 and 57 (February and June hatching dates, respectively). Figures 15 through 18, inclusive, graphically repre- sent the data presented in Tables 28 through 54, inclusive. These tables and figures compare percentages of individual egg sizes by hatching date. Whereas the Figures 19 and 21 represent, by hatching date, the complete egg size distri- bution data of Tables 55 and 57 (hatching dates February and June,respectively). The birds of the February hatching season produced a higher percentage of jumbo and extra-large eggs through- out the laying season than did the June-hatched birds. e at T c A: H. .. a up. 0 Cu 49 However, the June-hatched birds, at comparable ages pro- dliced a higher percentage of large, medium, small and pee- wee eggs. Again, the large, medium and small sized egg Ixroduction was affected by the season of lay for both tiatching seasons, with the percentage of medium eggs show- :ing the most fluctuation. The increases, in percentage, (of these sized eggs came during the periods of spring and summer months. Haugh unit scores of the eggs produced by the hens in the extended laying period are given in Tables 41 and 42. These tables are represented graphically by Figures 25 and 26. The average Haugh unit score of the eggs produced by the birds of the February-hatching season was 75.55 units. On the other hand, the June-hatched birds laid eggs that measured slightly higher or 74.77 Haugh units. The aver- age Haugh unit score of the eggs produced by the February- hatched birds represented fewer periods and these eggs were produced only during the later periods of the test, or Periods 46 through 65. The interior egg quality scores of the eggs of the June-hatched birds were averaged from Haugh scores recorded during Periods 57 through 66. There were no consistent advantages of interior egg quality of one season of hatch over another in this compar- ison. Comparable age of the bird and the season of egg 50 pxxaduction were observed per season of hatch as indicated izi Figures 25 and 26, respectively. The shell thickness data per season of hatch are given in Tables 45 and 44. These data are graphically Ixresented in Figures 27 and 28. There was no significant aadyantage of one hatching date over another in the egg sshell thickness quality factor. The shell thickness of 13he eggs produced by the hens of both seasons of hatch a w a a» a: .s A. c. n; 6. At {a .5 2 at I\\ a: a. 2. IV .A. T . «U :. ... w x 24 J: the same characteristic of producing higher numbers of eggs with blood spots during these seasons. The total egg production data, calculated in dozens of sized eggs per 1000 females, are given in Tables 48, 49 and 55. These data give the egg size distribution by hatching date (February and August). Tables 58 through 64, inclusive, give the egg size distribution of the hatching dates by individual egg weights. The August-hatched fe- males produced more dozens of small (512 dozen), peewee (155 dozen) and undergrade (207 dozen) eggs than the February-hatched females. The February-hatched females excelled in the production of the other weight classes of eeggs (jumbo, 551 dozen; extra-large, 1657 dozen; large, £940 dozen; and medium, 260 dozen). ESeason A (February hatch) versus Season E (October hatch) The total egg production data of females hatched in Ifebruary and October (Season A and E, respectively) are IIresented in Table l. The total egg production data are gfl?aphically represented by Figures 6 and 10. All seasons 01? hatch (the total egg production of the females hatched 31: six different seasons) are represented graphically by Figure 12. February-hatched females produced 4.9 eggs per fe- IIlale during the initial record period (12). On the other llalmi, October-hatched females produced 0.9 eggs per female c1tiring this first period. 55 The production mean of the February-hatched females 'was 9.27 eggs per female per two-week period, while the October—hatched females averaged 8.55 eggs per female per two-week period for the total record period. The higher rate of lay of the February-hatched females was reflected in'a sustained rate of lay of over 10 eggs per bird for 14 two-week periods. Compared to the above rate of lay, the October-hatched females maintained their egg produc- tion of over 10 eggs per bird for 10 two-week periods. Statistically analyzed, the difference in the pro- duction means of 0.74 eggs per female was significant (P (0.05, Tables 5 and 6). The February-hatched females peaked in egg produc- tion at 11.9 eggs per bird; Whereas, the October—hatched females reached a peak production of 12.2 eggs per bird :per two-week period. Individual egg size data of the females by hatching date are presented in Tables 28 through 54 and these tables are graphically represented in Figures 15 through 18. All llatching dates were compared by individual egg weights in ‘these tables and figures. Tables 55 and 59 present the total egg size distri— INition of the females hatched in February and October while “the same egg size distribution data are graphically re- IXresented in Figures 19 and 25. ..a Ca in c n v ‘. 56 The egg size distribution patterns, in Figures 15 through 18, inclusive, showed no consistent hatching date influences on the egg size distribution. There were season of production influences on the egg size distribution in the spring and summer months. Larger numbers of medium and large eggs were produced by the October-hatched females during those warmer months. The Haugh unit scores of the eggs produced by the females in the extended laying period are given in Tables 41 and 42 and these tables are represented graphically by Figures 25 and 26. The average Haugh units of the eggs produced by the February-hatched females was 75.55 units. 0n the other liand, the October—hatched females produced eggs averaging 74.75 Haugh units during the extended laying period. The eggs that were measured were produced by the February- liatched females when the birds were 92 weeks old. The October-hatched birds, when they were 58 weeks old, pro— duced the eggs that were measured. The Haugh unit records <3f the eggs of the February-hatched females terminated “flien the layers were 150 weeks old. On the other hand, the Haugh unit study of the October-hatched birds was dis- <3ontinued when the layers were 116 weeks old. The shell thickness data of the extended laying 19eriod are presented in Tables 45 and 44 and these data are represented graphically in Figures 27 and 28. The 57 shell thickness was not significantly different between the two hatching dates (February and October) during the extended laying period.‘ The eggs produced by the October and February-hatched females declined 0.0005 of an inch in shell thickness during the extended period of lay. The detectable blood Spot incidence data are pre- sented in Tables 45, 46 and 47 for all hatching dates. No significant differences were noted in the incidence of candled blood spots, when the egg production of the fe- males of the two hatching dates was compared. The seasonal ‘effect of larger numbers of blood spots found in eggs laid during the late summer, fall and early winter months was noted in the production of the females of both hatching dates (February and October). ' Total egg production data, calculated in dozens of sized eggs per 1000 females (hen-housed basis) are given in Tables 48, 49 and 55. These tables give the egg size distribution by hatching date. On the other hand, Tables 58 through 64, inclusiVe, give the egg size distribution data of the hatching dates by individual egg weights. Fewer dozens of eggs (5525 dozen) of all weight classes Were produced by the October-hatched females than by the February-hatched females (jumbo, 275 dozen; extra large, 1201 dozen; large, 1545 dozen; and medium,547 dozen). However, the production of undergrads and peewee eggs by females hatched on both dates were approximately the same. 58 Season A Februa hatch versus Season F (Decggber hatch) The total egg production data of females hatched in February and December (Seasons A and F, respectively) are ;presented in Table 1. The total egg production data for the comparison are graphically represented in Figures 6 and 11. All of the egg production data per hatching sea- son of the study are graphically represented in Figure 12. February—hatched females produced 4.9 eggs per fe- Inale during the first record period (Period 12) while the ZDecember-hatched females laid 9.0 eggs per female during ‘this first two-week period. The production means of the hatching dates under (zonsideration (February and December) were 9.27 and 8.01 eaggs, respectively, per female for the complete record 13eriod. The February-hatched females peaked in egg produc- ‘tion at 11.9 eggs per bird; whereas the December-hatched :females reached a peak of 10.8 eggs per bird per two-week 19eriod. The high rates of lay (10 or more eggs per bird) Jfor the February and December-hatched females were re- Iflected in 14 two-week periods and seven two-week periods, Irespectively. The difference between the production means of the :females hatched during these seasons was 1.26 eggs per female. Statistically analyzed, this difference was highly significant (Tables 5 and 6, P «0.01). 59 Individual egg size data per hatching date are pre- sented in Tables 28 through 54, inclusive, and these tables are graphically represented by Figures 15 through 18, in- clusive. All hatching dates (compared by separate egg weights) were represented in these figures. Tables 55 and 40 present the complete egg size dis- tribution of the egg production of the females hatched in February and December, respectively. The same egg size distribution data are graphically shown in Figures 19 and 24. It should be noted that the jumbo egg size distribu- tion percentage was higher for the February-hatched females ‘than for the December-hatched females for comparable peri- ods of lay. The same observation was made of the extra— Ilarge sized eggs which was in favor of the production of ‘the February-hatched females. The December-hatched females sstarted with a lower percentage in the production of large eeggs per comparable period of lay, but these birds peaked liigher than the February-hatched females. Season of pro- C1uction influences were again evident in the egg size dis- 1:ribution of the egg production of the females hatched on ‘these two dates. The production of large and medium—sized {Eggs was affected more by the season of production than VVere the other egg weights. The Haugh unit scores of the eggs produced by the females in the extended laying period are given in Tables 41 and 42 and these tables are represented graphically by 60 Figures 25 and 26. The average Haugh unit score of the eggs produced by the February-hatched females in the ex- tended lay period was 75.55 units and the December-hatched females produced eggs averaging 74.10 Haugh units. The Haugh unit scores of the eggs of the February—hatched fe- males were recorded when the females were from 92 to 150 weeks of age, while the eggs of the December—hatched birds were measured when the females were from 48 to 106 weeks of age. The shell thickness data of the laying period are ,presented in Tables 45 and 44 and are graphically repre— sented by Figures 27 and 28. The shell thickness of the eggs produced by the females of the February and December Inatching dates was not significantly different. Females of same age were involved in this measurement of egg quality. The detectable blood spot incidence data are pre- ssented in Tables 45, 46 and 47 for all hatching dates. No :significant differences were noted in the numbers of can- tiled blood spots in the eggs produced by the females of ‘these hatching dates. The seasonal effects of larger num- ‘bers of blood spots occurring during the late summer, fall and early winter months were noted in the eggs produced by females of both hatching dates. However, during these sea- sons of lay the following year, larger numbers of blood 61 spots were not noted and not eXplained in the eggs produced *by the December-hatched females. Total egg production data, calculated in dozens of eggs per 1000 females (hen-housed basis) are presented in Tables 48, 49 and 56.. These tables of data give the egg size distribution by hatching date. On the other hand, Tables 58 through 64 give the egg size distribution data ;per hatching date by individual egg weights. The February- hatched females produced more dozens of jumbo (581 dozen), extra-large (2612 dozen), and medium (1415 dozen) eggs 'than the December-hatched females. Season B (April hatch) versus Season 0 (June hatch) The date of the total egg production per female Ihatched in April and in June are presented in Table l. iIhe data indicate the average number of eggs produced per .female per two-week period and are graphically represented :in Figures 7 and 8. All egg production data per season «are shown graphically, for comparative purposes, by Figure 12. The females hatched in April laid at the rate of 1.9 eggs per bird during Period 12 in comparison with a rate of 1.0 egg per bird for the same period by the females hatched in June. The April-hatched birds peaked in egg production per period at 10.6 eggs per bird; whereas, the June-hatched his». » 62 birds reached a peak production of 12.2 eggs per bird. The persistency of egg production over 10 eggs per bird was four two-week periods for the April-hatched females and six two-week periods for the June-hatched birds. The total egg production mean of the April-hatched females was 7.47 eggs per bird and the production mean of the June-hatched females was 7.67 eggs per bird. Analysis of variance and Duncan's Multiple Range testing indicated that the difference in the egg production means of 0.20 eggs per bird was not significant (Table 6). The individual egg size distribution data of the fe- inales by hatching date are presented in Tables 28 through 343 and these tables are graphically represented in Figures .13 through 18. Each hatching season was compared by sepa- Jrate egg weights in these tables and figures. On the other hand, Tables 56 and 57 Present the isotal egg distribution of the females hatched in April and Jaime. The same egg weight data of the females hatched at 1311ese two dates are graphically represented by Figures 20 aJnd 21. The females of both hatching seasons produced eggs 'tlaat were distributed according to identical weights dur- 5dug the laying periods (Tables 56 and 57). However, dur- ing the extended lay periods the females of both hatching (iates produced larger numbers of medium and large eggs in 65 in the spring and summer months. The increase in percent- age of these egg sizes was offset by decreases in the per- centage of the jumbo and extra-large eggs during these months. The Haugh unit scores of the eggs produced by the females in the extended lay periods are given in Tables 41 and 42 and these tables are represented graphically by Figures 25 and 26. The average Haugh unit score of the eggs produced by the April-hatched females measured 76.46 1inits, while the June-hatched females produced eggs aver- aging 74.77 Haugh units during the extended lay period. There were no important differences in the Haugh units of ‘the eggs produced by the females of either hatching season shown in Table 41. - Shell thickness data of the eggs produced during ‘the extended lay periods are presented in Tables 45 and 44 51nd are represented graphically by Figures 27 and 28. The sshell thickness egg quality factor was not noticeably dif— errent between the egg production of the females of either Inatching date. The shell thickness declined approximately (3.0005 of an inch during the extended lay periods (Figure 228). The detectable blood spot incidence data of the eggs produced by the April-hatched and June-hatched females are presented in Tables 45, 46 and 47. Small numbers (ex- pressed in percentages) of blood spots were noted in most 64 periods of lay. However, a higher percentage of blood spots occurred during the later summer, fall and early ‘winter months (Table 45). Females, representing both hatching dates showed the same characteristics of produc- ing a higher percentage of eggs with blood spots during these seasons. Total egg production data calculated in cumulative dozens of sized eggs per 1000 females (hen-housed basis) are given in Tables 48, 50 and 52. These data give the egg size distribution in cumulative dozens produced by females of the comparative hatching dates (April and June). On the other hand, Tables 58 through 64 give the cumulative egg size distribution data by individual egg weights. The April hatched females produced a larger number of dozens of jumbo (66 dozen) and extra-large eggs (518 (dozen) at the beginning of the record periods than the June- liatched females. The differences were not evident toward ‘the close of the record periods. More dozens of large eggs (1574 doZen) were produced in the later periods of lay by the June—hatched females than by the April—hatched females. The production of large eggs started at essen- tially the same time for these two groups of females. The June-hatched females produced significantly larger numbers of medium (1956 dozen) eggs than the April-hatched females. No differences in egg production by hatching date were 65 observed in the small and peewee weight classifications as shown in Tables 62 and 65. Season B (April hatch) versus Season D (Auggst hatch) The total egg production data per female hatched in April and August are presented in Table l. The data presented indicate the average numbers of eggs produced per female (hen-day basis) per two-week period and are graphically represented by Figures 7 and 9 and for com- parative purposes by Figure 12. The April-hatched females laid at the rate of 1.9 eggs per bird during the initial record Period 12. Whereas, the August-hatched females laid at the rate of 5.4 eggs per bird during the comparable period. The April-hatched females peaked in egg production at 10.6 eggs per bird; whereas, the August-hatched birds reached a peak egg production of 12.0 eggs per bird. Over 10 eggs per period were produced for four two-week periods by the April-hatched birds; however, the August-hatched birds produced over 10 eggs per period for seven two—week periods. The total egg production mean of the April-hatched females was 7.47 eggs per bird. 0n the other hand, the production mean of the August-hatched birds was 8.15 eggs per bird. Analysis of variance and Duncan's Multiple Range testing indicated that the difference in the egg production means of 0.68 eggs was not significant (Table 6). 66 The individual egg size distribution data of the seasonally-hatched females are presented in Tables 28 through 54 and are graphically represented in Figures 15 through 18. On the other hand, Tables 56 and 58 present the complete egg size distribution of the females by hatch- ing date. The same egg weight data of these seasonally hatched females are graphically represented by Figures 20 and 22. The females of the April and the August hatching season produced a size distribution of eggs that, when the data were plotted, indicated a similar pattern of egg size distribution as shown in Figures 15 through 18. However, during the extended lay periods the females of both hatch- ing dates produced a pattern of egg size distribution that was affected by season of production. Higher percentages of large and medium eggs were produced and lower percent- ages of jumbo and extra-large eggs produced during the spring and summer months. The Haugh unit scores of the eggs produced by the females in the extended lay periods are presented in Tables 41 and 42 and are represented graphically by Figures 25 and 26. The average Haugh unit score of the eggs produced by the April-hatched females measured 76.46 units and the August-hatched females produced eggs averaging 74.07 Haugh units during the extended lay period. The season of pro- duction did not affect the Haugh units of the eggs produced 67 by the seasonally—hatched birds, illustrated by Table 41. Shell thickness data of the eggs produced by~the hens in the extended lay periods are presented in Tables 45 and 44 and are graphically represented in Figures 27 and 28.- There were no seasonal differences in the shell thickness of the eggs produced by the females of either hatching season and the shell thickness of these eggs did decline (0.0005 of an inch) over time during the extended lay periods, as shown in Table 45 and Figure 28. Detectable blood spot incidence data of the eggs produced by the April-hatched and August-hatched females are presented in Tables 45, 46 and 47. Insignificant num- bers of blood spots were noted in most periods of lay. However, a higher percentage of blood spots occurred during the late summer, fall and early winter months. Both groups of seasonally-hatched hens showed the same characteristic of producing a higher percentage of eggs with blood spots during these seasons. Total egg production data, calculated in cumulative dozens of sized eggs per 1000 (hen—housed basis) are pre- sented in Tables 48, 50 and 55. These tables show the egg Size distribution of monthly cumulative dozens of eggs pro- duced by females of the comparative hatching dates. Where- as, Tables 58 through 64 show the cumulative egg size dis- tribution data by separate egg weights and per season of hatch. 68 The August—hatched females produced larger numbers of dozens of eggs (5554 dozen) than the April-hatched fe- males. This Table 48 also indicated that the rate of in- crease in egg production was higher for the August-hatched birds. The tables of individual egg weights, Tables 58 through 64, inclusive, indicated that the April-hatched females had produced comparable or more dozens of eggs (jumbo, 54 dozen; extra-large, 255 dozen; and large, 558 dozen) at 10 months of cumulate egg production. However, the August-hatched females had excelled the April—hatched females in the weight classifications of jumbo (22 dozen), extra—large (1041 dozen) and large (1556 dozen) eggs by the end of the test. The August—hatched females also pro- duced more dozens of medium (1495 dozen), small (749 dozen) and peewee (54 dozen) eggs. Sgason B (April hatch) versus Sea§pn E (October hatch) The total egg production data per female hatched in April and October are presented in Table l. The data pre- sented indicate the average numbers of eggs produced per female (hen-day basis) per two—week period. These data are graphically represented by Figures 7 and 10 and for comparative purposes in Figure 12. The April—hatched females laid at the rate of 1.9 eggs per bird during the initial record Period 12. On the other hand, the October-hatched females laid at the rate 6f 0.9 eggs per bird during the similar period. 62 birds reached a peak production of 12.2 eggs per bird. The persistency of egg production over 10 eggs per bird was four two-week periods for the April-hatched females and six two-week periods for the June-hatched birds. The total egg production mean of the April-hatched females was 7.47 eggs per bird and the production mean of the June-hatched females was 7.67 eggs per bird. Analysis of variance and Duncan's Multiple Range testing indicated that the difference in the egg production means of 0.20 eggs per bird was not significant (Table 6). The individual egg size distribution data of the fe- males by hatching date are presented in Tables 28 through 34, and these tables are graphically represented in Figures 15 through 18. Each hatching season was compared by sepa- rate egg weights in these tables and figures. On the other hand, Tables 56 and 57 present the total egg distribution of the females hatched in April and Jiine. The same egg weight data of the females hatched at tliese two dates are graphically represented by Figures 20 811d 21. 5 The females of both hatching seasons produced eggs tfllat were distributed according to identical weights dur- 3Lng the laying periods (Tables 56 and 57). However, dur— ing the extended lay periods the females of both hatching dates produced larger numbers of medium and large eggs in 65 in the spring and summer months. The increase in percent- age of these egg sizes was offset by decreases in the per— centage of the jumbo and extra—large eggs during these months. The Haugh unit scores of the eggs produced by the females in the extended lay periods are given in Tables 41 and 42 and these tables are represented graphically by Figures 25 and 26. The average Haugh unit score of the eggs produced by the April-hatched females measured 76.46 units, while the June-hatched females produced eggs aver- aging 74.77 Haugh units during the extended lay period. There were no important differences in the Haugh units of the eggs produced by the females of either hatching season shown in Table 41. > Shell thickness data of the eggs produced during the extended lay periods are presented in Tables 45 and 44 and are represented graphically by Figures 27 and 28. The shell thickness egg quality factor was not noticeably dif- ferent between the egg production of the females of either llatching date.' The shell thickness declined approximately C>.OOO5 of an inch during the extended lay periods (Figure 28). The detectable blood Spot incidence data of the eggs produced by the April-hatched and June—hatched females are presented in Tables 45, 46 and 47. Small numbers (ex- pressed in percentages) of blood spots were noted in most . u a . P, wllfl“ a .9. I I . u titihvnnt periods of lay. However, a higher percentage of blood spots occurred during the later summer, fall and early winter months (Table 45). Females, representing both hatching dates showed the same characteristics of produc- ing a higher percentage of eggs with blood spots during these seasons. Total egg production data calculated in cumulative dozens of sized eggs per lOOOermales (hen-housed basis) are given in Tables 48, 50 and 52. These data give the egg size distribution in cumulative dozens produced by females of the comparative hatching dates (April and June). 0n the other hand, Tables 58 through 64 give the cumulative egg size distribution data by individual egg weights. The April hatched females produced a larger number of dozens of jumbo (66 dozen) and extra-large eggs (518 dozen) at the beginning of the record periods than the June- liatched females. The differences were not evident toward the close of the record periods. More dozens of large eggs (1574 dOzen) were produced in the later periods of lay by the June-hatched females than by the April—hatched females. The production of large eggs started at essen- tially the same time for these two groups of females. The June-hatched females produced significantly larger numbers of medium (1956 dozen) eggs than the April-hatched females. No differences in egg production by hatching date were ghl 65 observed in the small and peewee weight classifications as shown in Tables 62 and 65. Season B A ril hatch versus Season D Au st hatch The total egg production data per female hatched in April and August are presented in Table l. The data presented indicate the average numbers of eggs produced per female (hen-day basis) per two-week period and are graphically represented by Figures 7 and 9 and for com- parative purposes by Figure 12. The April-hatched females laid at the rate of 1.9 eggs per bird during the initial record Period 12. Whereas, the August—hatched females laid at the rate of 5.4 eggs per bird during the comparable period. The April-hatched females peaked in egg production at 10.6 eggs per bird; whereas, the August-hatched birds reached a peak egg production of 12.0 eggs per bird. Over 10 eggs per period were produced for four two-week periods by the April-hatched birds; however, the August-hatched birds produced over 10 eggs per period for seven two-week periods. The total egg production mean of the April-hatched females was 7.47 eggs per bird. On the other hand, the production mean of the August-hatched birds was 8.15 eggs per bird. Analysis of variance and Duncan's Multiple Range testing indicated that the difference in the egg production means of 0.68 eggs was not significant (Table 6). ,A g m V‘ Q723¥|h£vfi . 3'11... ** . 7"?” ',' “w" ,vo'f- _- .. . w. ._ , .4 - ‘ ““3”“. ”it .1, .. we. W - -.-I--*- r . , -, fig ,, “in” I, .77. ff." ,- . . z t f \ e . 1? _fi _ , ~ "““1‘ ,7, W 5 w~W¢ 66 The individual egg size distribution data of the seasonally-hatched females are presented in Tables 28 through 54 and are graphically represented in Figures 15 through 18. On the other hand, Tables 56 and 58 present the complete egg size distribution of the females by hatch- ing date. The same egg weight data of these seasonally hatched females are graphically represented by Figures 20 and 22. The females of the April and the August hatching season produced a size distribution of eggs that, when the data were plotted, indicated a similar pattern of egg size distribution as shown in Figures 15 through 18. However, during the extended lay periods the females of both hatch— ing dates produced a pattern of egg size distribution that Was affected by season of production. Higher percentages of large and medium eggs were produced and lower percent- ages of jumbo and extra-large eggs produced during the spring and summer months. The Haugh unit scores of the eggs produced by the females in the extended lay periods are presented in Tables 41 and 42 and are represented graphically by Figures 25 and 26. The average Haugh unit score of the eggs produced by the April-hatched females measured 76.46 units and the August-hatched females produced eggs averaging 74.07 Haugh units during the extended lay period. The season of pro- duction did not affect the Haugh units of the eggs produced 67 by the seasonally-hatched birds, illustrated by Table 41. Shell thickness data of the eggs produced by the hens in the extended lay periods are presented in Tables 45 and 44 and are graphically represented in Figures 27 and 28.’ There were no seasonal differences in the shell thickness of the eggs produced by the females of either hatching season and the shell thickness of these eggs did decline (0.0005 of an inch) over time during the extended lay periods, as shown in Table 45 and Figure 28. Detectable blood spot incidence data of the eggs produced by the April-hatched and August-hatched females are presented in Tables 45, 46 and 47. Insignificant num- bers of blood spots were noted in most periods of lay. However, a higher percentage of blood spots occurred during the late summer, fall and early winter months. Both groups of seasonally-hatched hens showed the same characteristic of producing a higher percentage of eggs with blood spots during these seasons. Total egg production data, calculated in cumulative dozens of.sized eggs per 1000 (hen-housed basis) are pre- sented in Tables 48, 50 and 55. These tables show the egg Size distribution of monthly cumulative dozens of eggs pro- duced by females of the comparative hatching dates. Where- as, Tables 58 through 64 show the cumulative egg size dis- tribution data by separate egg weights and per season of hatch. IIIIIII._________________________________________________ 68 The August-hatched females produced larger numbers of dozens of eggs (5554 dozen) than the April-hatched fe— males. This Table 48 also indicated that the rate of in- crease in egg production was higher for the August—hatched birds. The tables of individual egg weights, Tables 58 (through 64, inclusive, indicated that the April-hatched females had produced comparable or more dozens of eggs (jumbo, 54 dozen; extra—large, 255 dozen; and large, 558 dozen) at 10 months of cumulate egg production. However, the August—hatched females had excelled the April-hatched females in the weight classifications of jumbo (22 dozen), extra-large (1041 dozen) and large (1556 dozen) eggs by the end of the test. The August-hatched females also pro- duced more dozens of medium (1495 dozen), small (749 dozen) and peewee (54 dozen) eggs. §gason B (April hatch) versus Season E (October hatch) The total egg production data per female hatched in April and October are presented in Table l. The data pre- sented indicate the average numbers of eggs produced per female (hen—day basis) per two-week period. These data are graphically represented by Figures 7 and 10 and for comparative purposes in Figure 12. The April-hatched females laid at the rate of 1.9 eggs per bird during the initial record Period 12. On the Other hand, the October-hatched females laid at the rate or 0.9 eggs per bird during the similar period. More”... ‘. .. '17“ ‘ ,x-h“ .- u ”~22“- 11“” . '3' 35‘7". , 69 The April-hatched females peaked in egg production per layer per period at 10.6 eggs; whereas, the October- hatched birds reached a peak egg production of 12.2 eggs per bird. Over 10 eggs per bird were produced for four two-week periods by the April-hatched birds; whereas, the October-hatched birds produced over 10 eggs per period for 10 consecutive periods. The total egg production means were 7.47 and 8.55 eggs per bird hatched in April and October. Analysis of variance and Duncan's Multiple Range Tests indicated that the difference in means of 1.06 eggs per bird per period was highly significant, (P <0.01, Tables 5 and 6). The individual egg size distribution data of the females hatched at different times (April and October) are presented in Tables 28 through 54, inclusive, and are graphically represented by Figures 15 through 18, inclu- sive. Tables 56 and 59 tabulate the complete egg size distribution data of the females hatched in April and October and the same egg weight data are graphically shown 'by'Figures 20 and 25. The females of both hatching seasons (April and October) produced a size distribution of eggs that, when ‘the data were graphically represented, the figures ap- Peared to be essentially similar as shown in Figures 15 through 18, inclusiVe. The differences in level of the percentage lines on the representative graphs indicate 70 that a higher percentage of extra-large eggs were produced by the October—hatched females. The level of the large egg percentage line of the egg production of the October— hatched birds was only slightly higher than the April- hatched birds. Differences,in the balance of the weight (classifications, were not significant between the egg pro- duction of the two seasonally-hatched females. However, during the extended lay periods, the fe- males of both hatching dates produced eggs that were af- fected by the season of production. There were higher percentages of large and medium eggs and lower percentages of jumbo and extra-large eggs produced during the spring and summer months. Haugh unit scores of the eggs produced by the fe- males in the extended lay periods are presented in Tables 41 and 42 and are represented graphically by Figures 25 and 26. The average Haugh unit score of the eggs produced by the April-hatched females measured 76.46 units. On the other hand, the October-hatched females produced eggs averaging 74.75 Haugh units during the extended lay period. There were no season of production effects in the Haugh units of the eggs produced by the seasonally-hatched birds. The shell thickness data of the eggs produced by the hens in the extended lay periods are presented in Tables 45 and 44 and are represented graphically in Fig- Ures 27 and 28. Season of production did not affect the 71 shell thickness of the eggs produced by the females of either hatching date, illustrated in Table 45. The shell thickness of the eggs laid during the extended lay period declined approximately 0.0005 of an inch. The detectable blood spot incidence data of the eggs produced by the April and October-hatched females are given in Tables 45, 46 and 47. Insignificant numbers of blood spots were observed in most periods of lay. However, a higher percentage of blood spots occurred during the late summer, fall and early winter months shown.in Table 45. Both groups of seasonally—hatched birds produced a higher percentage of blood spots during these seasons of lay. Total egg production data, calculated in cumulative dozens of sized eggs per 1000 females (hen-housed basis) are presented in Tables 48, 50 and 55. These tables give the egg size distribution in monthly cumulative dozens of eggs produced by females of the hatching dates being com- pared. Differently presented, Tables 58 through 64 give the cumulative separate egg size distribution data season of hatch. The October-hatched females produced 5525 more dozens of eggs than the April-hatched females. Of the vari- ous egg size classifications, the October-hatched females produced more dozens of eggs than the April—hatched females With the following egg sizes: jumbo (155 dozen); extra- large (1288 dozen); large (990 dozen); and medium (1519 72 dozen). More dozens of small eggs (120 dozen) and of pee- wee eggs (86 dozen) were produced by the April-hatched fe- males than by the October-hatched females in comparable months. Season B (April hatch) versus Season F (December hatch) The total egg production data per female hatched in April and December are presented in Table l. The-data presented indicate the average numbers of eggs produced per female (hen—day basis) per two—week period. These data are graphically represented by Figures 7 and 11, and for comparative purposes by Figure 12. The April-hatched females laid at the rate of 1.9 eggs per bird during Period 12. During the same initial record period, the December-hatched females laid 9.0 eggs per bird. The April-hatched females peaked in egg production per layer per period at 10.6 eggs; whereas, the December- hatched birds reached a peak egg production of 10.8 eggs per bird. [Over 10 eggs per bird were produced for four two-week periods by the April-hatched birds. On the other hand, the December-hatched females produced over 10 eggs per period for seven consecutive two-week periods. The total egg production means were 7.47 and 8.01 eggs per bird hatched in April and December. Analysis of Variance and Duncan's Multiple Range tests indicated that f, ., —‘~' ‘2‘?" ... $1.. 1.1. 5. e. . 75 the difference in means of 0.54 eggs per bird was not significant (Tables 5 and 6). The individual egg size distribution data of the females hatched at different times are presented in Tables 28 through 54, inclusive, and are graphically represented by Figures 15 through 18, inclusive. Whereas, Tables 56 and 40 list the complete egg size distribution data of the females. The same egg weight data of these April and December-hatched females are graphically shown by Figures 20 and 24. The April—hatched females produced a higher percent— age of jumbo, extra—large and large eggs at the beginning of the record periods than did the December-hatched fe— males. However, the December—hatched females peaked at a higher percentage of extra—large and large eggs than the April—hatched females. These peaks were achieved at an older age also. The medium egg size distribution pattern of both the April and December-hatched females were essen— tially the same. Seasonal production effects on the medium egg size distribution in the extended lay periods were again evident for both seasons of hatch, and shown in Fig— ure 16. Small egg percentages were lower for the December- hatched females and these birds persisted longer in produc- ing small eggs as represented in Figure 17. The Haugh unit scores of the eggs produced by the females in the extended lay periods are presented in 74 Tables 41 and 42 and are represented graphically by Fig- ures 25 and 26. The\average Haugh unit score of the eggs produced by the April-hatched females measured 76.46 units. Whereas, the Decemberehatched females produced eggs aver- aging 74.10 Haugh units during the extended lay period. There were no seasonal production effects in the Haugh units of the eggs produced by the seasonally-hatched birds (Table 41). Shell thickness data of the eggs produced by the hens and in the extended lay periods are presented in Tables 45 and 44 and are graphically represented by Fig- ures 27 and 28. Season of production did not affect the shell thickness of the eggs produced by the April and December—hatched birds, illustrated by Table 45. The shell thickness of the eggs laid during the extended lay periods declined approximately 0.0005 of an inch. The detectable blood spot incidence data of the eggs produced by the April and December-hatched females are given in Tables 45, 46 and 47. A low percentage (l-2%) of blood spots was detected in most periods of lay repre- senting both hatching dates. However, a higher percent- age (2—5%) of blood spots was noted in Table 45 for the late summer, fall and early winter months. Total egg production data (hen-housed basis),calcu- lated in cumulative dozens of sized eggs per 1000 females, are presented in Tables 48, 50 and 56. Tables 58 through 75 64 give the cumulative individual egg weight distribution data per season of hatch. More dozens of eggs of all weight classifications (2187 dozen) were produced by the December-hatched females than by the April-hatched birds. The egg production of the females of both seasons of hatch was relatively simi- lar in the egg weights of jumbo, extra—large, large and medium. However, the December-hatched females produced 1504 more dozens of small eggs and 818 more dozens of peewee eggs than the April-hatched birds. Sgason C (Jung hatch) versus Season D (August hatch) The total egg production data per female hatched in June and August are presented in Table l. The data presented indicate the average numbers of eggs (hen—day basis) produced per female per two-week period. These data are graphically represented by Figures 8 and 9 and for comparative purposes by Figure 12. The June—hatched females laid at the rate of 1.0 eggs per bird during Period 12. During the same initial record period, the August—hatched females laid 5.4 eggs per bird. The June-hatched females peaked in egg production per layer per period at 12.2 eggs, whereas, the August- hatched females reached a peak egg production of 12.0 eggs per bird. The June-hatched birds persisted in the produc- tion of over 10 eggs per bird per period for six two-week 76 periods. 0n the other hand, the August-hatched birds pro— duced over 10 eggs per period for seven consecutive two- week periods. The total egg production means were 7.67 and 8.15 eggs per bird hatched in June and August, respectively. Analysis of variance and Duncan's Multiple Range Tests in- dicated that the difference in means of 0.48 eggs per bird was not significant (Tables 5 and 6). The individual egg size distribution data of the June and August—hatched females are presented in Tables 28 through 54, inclusive, and are graphically represented in Figures 15 through 18. Tables 57 and 58 present the com- plete egg size distribution data of the June and August- hatched females and these data are graphically represented by Figures 21 and 22. The June and August-hatched females produced egg sizes that, when these data were plotted on Figures 15 through 18, represented essentially a similar pattern of egg size distribution. Season of production influences on the production of medium eggs were evident in the ex- tended lay periods. Haugh unit scores of the eggs produced by the fe- males in the extended lay periods are presented in Tables 41 and 42 and are represented graphically by Figures 25 and 26. The average Haugh unit score of the eggs produced by the June-hatched females measured 74.77 units and the 77 eggs of the August-hatched birds measured an average of 74.07 Haugh units during the extended lay period. There were no seasonal production effects on the Haugh units of the eggs produced by the June and August-hatched birds. Shell thickness data of the eggs produced by the hens in the extended lay periods are presented in Tables 45 and 44 and are represented graphically by Figures 27 and 28. Season of production did not affect the shell thickness of the eggs produced by the June and August- hatched birds shown in Table 45. The shell thickness of the eggs laid during the extended lay periods did decline approximately 0.0005 of an inch. Detectable blood spot incidence data of the eggs produced by the June and August-hatched females are given in Tables 45, 46 and 47. A low percentage (1%) of blood spots was detected in most periods of lay of the June and August—hatched birds. However, a higher percentage (5-4%) of blood spots was noted during the late summer, fall and early winter months and shown in Table 45. The June and August-hatched females both showed this characteristic during these seasons. Total egg production data (hen-housed basis), cal- culated in cumulative dozens of egg sizes per 1000 females, are presented in Tables 48, 52 and 55. Tables 58 through 64 give the cumulative individual egg weight distribution data per hatching season. 78 p More dozens of eggs (1996 dozen) of all weights were produced by the August-hatched females than the June- hatched females. The egg production of the August-hatched females yielded more dozens of jumbo (91), extra-large (687), large (244), small (802), peewee (94) and undergrads (508) eggs than the June-hatched birds. The June-hatched birds did produce 450 dozen eggs more than the August- hatched birds. Season 0 (June hatch) versus Season E (October hatch) The total egg production data per female hatched in June and October are presented in Table l. The data presented indicate the average numbers of eggs (hen-day basis) produced per female per two-week period. These data are graphically represented by Figures 8 and 10 and for comparative purposes by Figure 12. The June-hatched females laid at the rate of 1.0 eggs per bird during Period 12. Whereas, the October- hatched females laid 0.9 eggs per bird during the same period. Both the June-hatched and October-hatched females Peaked in egg production per layer per period at 12.2 eggs. The June-hatched birds persisted in egg production of over 10 eggs per bird per period for six periods. On the other hand, the October-hatched birds produced over 10 eggs per Period for 10 consecutive periods. 79 The total egg production means were 7.67 and 8.55 eggs per bird hatched in June and October, respectively. Analysis of variance and Duncan's Multiple Range tests indicated that the difference in means of 0.86 eggs per bird was significant (P <0.05, Tables 5 and 6). The individual egg size distribution data of the June and October-hatched females are presented in Tables 28 through 54, inclusive, and are graphically represented in Figures 15 through 18, inclusive. Similarly, Tables 57 and 59 present the complete egg size distribution data of the June and 0ctober-hatched females and these data are graphically represented by Figures 21 and 25. The June and October-hatched females produced an egg size distribution pattern that was essentially the same shape, illustrated in Figures 15 through 18. However, the level of the egg size distribution curve of the jumbo and extra-large eggs produced by the October-hatched birds was higher. vThe large-egg curves produced by females of both Iiatching dates were essentially similar. Whereas, the (data indicated that the June-hatched females produced a lligher percentage of medium and small eggs. Season of Irroduction influences on the production of medium eggs in the extended lay periods were again evident in the curves Of Figure 16. The Haugh unit scores of the eggs produced by the females in the extended lay periods are presented in Tables L—___— 80 41 and 42 and are represented graphically in Figures 25 and 26. The average Haugh unit score of the eggs produced by the June—hatched females measured 74.7? units while the eggs of the October-hatched females measured an average of 74.75 Haugh units during the extended lay periods. There were no seasonal production effects on the Haugh units of the eggs produced by the June and October-hatched birds. The shell thickness data of the eggs produced by the hens in the extended lay periods are presented in Tables 45 and 44 and are represented graphically by Figures 27 and 28. Season of production did not affect the shell thickness of the eggs produced by the June and October- hatched birds, shown in Table 45. The shell thickness of the eggs laid during the extended lay periods declined ap- proximately 0.0005 of an inch. The detectable blood spot incidence data of the eggs produced by the June and October-hatched females are given in Tables 45, 46 and 47. Low percentages (1%) of 'blood spots were detected in most periods of lay of the «June and October—hatched birds. However, a higher percent- éige (3-4%) was produced by the June—hatched birds and a Slightly lower percent (2-5%)tw*the October-hatched birds during the late summer, fall and early winter months as Shown in Table 45. Total egg production data (hen-housed basis), cal— culated in cumulative dozens of egg sizes per 1000 birds, 81 are presented in Tables 48, 52 and 55. Tables 58 through 64 give the cumulative individual egg weight distribution data per hatching season. The October-hatched birds produced 585 more dozens of eggs than the June-hatched birds. The October-hatched females produced more dozens of jumbo and extra-large eggs fbut fewer dozens of large, medium, small and peewee eggs 'than did the June-hatched birds as listed in Tables 52 and 55. ESeason C {June hatch) versus Season F (Decggber hatch) The total egg production data per female hatched :in June and December are presented in Table l. The data lpresented indicate the average numbers of eggs (hen-day laasis) produced per female per two-week period. These data are graphically represented by Figures 8 and 11 and for comparative purposes by Figure 12. The June-hatched females laid at the rate of 1.0 «eggs per bird during Period 12, whereas, the December- llatched females laid 9.0 eggs per bird during the same period. The June-hatched females peaked in egg production IDeI~layer per two-week period at 12.2 eggs, and the December-hatched females reached a peak egg production of 10.8 eggs. The June—hatched birds maintained a level of egg production of over 10 eggs per bird per period for six 82 periods. On the other hand, the December-hatched birds laid at this level for seven consecutive periods. The total egg production means were 7.67 and 8.01 eggs per bird hatched in June and December, respectively. Analysis of Variance and Duncan's Multiple Range tests indicated that the difference in means of 0.54 eggs per bird was not significant (Tables 5 and 6). The individual egg size distribution data of the June and December-hatched females are presented in Tables 28 through 54 and are graphically represented in Figures- 15 through 18. Similarly, Tables 57 and 40 present the complete egg size distribution data of the June and December—hatched females and are graphically represented by Figures 21 and 24. The jumbo egg size distribution patterns of eggs laid by females of both seasons of hatch were essentially alike. However, the extra-large and large egg size dis— tribution patterns were not similar. The December-hatched females laid a lower percentage of extra-large and large eggs than the June-hatched females. Season of production effects influenced the production of the eggs of both fifleights, however, as the production of large and extra- large eggs was depressed in the spring and summer months. During the same months, more medium eggs were produced by both the June-hatched and December-hatched females. There Were differences between hatching dates in the small egg H 011 .1. Hpn y‘i‘ .Yu‘r‘fl [\ l ‘ 85 percentage curves. The December-hatched females produced a lower percentage of Small eggs during the early periods and these layers persisted for a longer period of time in the production of small eggs (Figure 17). The Haugh unit scores of the eggs produced by the females in the extended lay periods are presented in Tables 41 and 42 and are represented graphically by Figures 25 and 26. The average Haugh unit score of the eggs produced by the June-hatched females measured 74.77 units while the December-hatched females produced eggs averaging 74.10 Haugh units during the extended lay periods. The shell thickness data of the eggs produced by the hens in the extended lay periods are presented in Tables 45 and 44 and are graphically represented by Figures 27 and 28. Season of production did not affect the shell thickness of the eggs produced by the June and December- hatched females, shown in Table 45. The shell thickness of the eggs laid during the extended lay periods declined approximately 0.0005 of an inch. The blood spot incidence data of the eggs produced by the June and December-hatched females are given in Tables 45, 46 and 47. A low percentage (1%) of blood Spots was detected in most periods of lay. However, a higher percentage (5-4%) was produced by the June—hatched birds and a lower percentage (2-5%) was produced by the December-hatched birds during the late summer, fall and J‘—, 84 early winter which is illustrated in Table 45. Total egg production data (hen-housed basis), cal- culated in cumulative dozens of egg sizes per 1000 birds, are presented in Tables 48, 52, and 56. Tables 58 through 64 present the cumulative individual egg weight distribu- tion data per hatching season. The June-hatched females produced 446 more dozens of eggs than the December-hatched birds. The June—hatched females produced more dozens of jumbo eggs (74 dozen), ‘ extra-large eggs (676 dozen), large eggs (1185 dozen) and medium eggs (1271 dozen) than the December—hatched females. On the other hand, the December-hatched females produced more small eggs (1572 dozen), peewee eggs (958 dozen) and undergrade eggs (450 dozen) than the June—hatched birds. §§g§9n D (August hatch) versus Sggggn E (October hatch) The total egg production data per female hatched in August and October are presented in Table l. The data .presented indicate the average numbers of eggs (hen—day laasis) produced per female per two-week period. These (iata are graphically represented by Figures 9 and 10 and for comparative purposes by Figure 12. The August-hatched females laid at the rate of 5.4 eggs per bird during the initial record period (12), while the October-hatched females laid 0.9 eggs per bird during the same period. 85 The August-hatched females peaked in egg production per layer per two-week period at 12.0 eggs, and the October-hatched females reached a peak egg production of 12.2 eggs per bird. The August-hatched birds maintained a level of egg production of over 10 eggs per bird per period for seven periods while the October-hatched birds produced over 10 eggs per period for 10 consecutive periods. The total egg production means were 8.15 and 8.55 eggs per bird hatched in August and October, respectively. Analysis of Variance and Duncan's Multiple Range tests indicated that the mean difference of 0.58 eggs per bird was not significant (Tables 5 and 6). The individual egg size distribution data of the August and October-hatched females are presented in Tables 28 through 54, inclusive, and are graphically represented by Figures 15-18, inclusive. Similarly, Tables 58 and 59 pIesent the complete egg size distribution data of the .August and October-hatched females and are graphically re- I>resented by Figures 22 and 25. The percentage of jumbo and extra-large eggs was 1ligher for the eggs laid by the October-hatched females thanby the August—hatched females. The egg size distri- ‘bution patterns of the large, medium and small egg weights Were essentially similar except for the influences of the Season of production. Higher percentages of eggs of these . 86 egg weights were laid during the spring and summer months by the females of both the August and October-hatched females, as shown in Figures 15, 16 and 17. The Haugh unit scores of the eggs produced by the females in the extended lay period are presented in Tables 41 and 42 and are graphically represented by Figures 25 and 26. The average Haugh unit score of the eggs produced by the August-hatched females measured 74.07 units while the October-hatched females produced eggs averaging 74.75 Haugh units during the extended lay periods. The shell thickness data of the eggs produced by the hens in the extended lay periods are presented in Tables 45 and 44 and are graphically represented by Figures 27 and 28. Season of egg production did not affect the shell thickness of the eggs produced by the August and October-hatched females, as shown in Table 45. The shell thickness of the eggs laid during the extended lay periods did decline approximately 0.0005 of an inch. The detectable blood spot incidence data of the eggs gproduced by the August and October-hatched females are given in Tables 45, 46 and 47. A low percentage (1%) of blood spots was detected in most periods of lay. However, a higher percentage (2-5%) of blood spots was produced by the August and October-hatched females during the late sum— mer, fall and early winter months, as recorded in Table 45. 87' The total egg production data, calculated in cumu- lative dozens of egg sizes per 1000 layers, (hen-housed basis) are presented in Tables 48, 55 and 55. Tables 58 through 64 present the cumulative individual egg weight distribution data per hatching season. The August-hatched females produced 1281 more dozens of eggs than the October-hatched birds as shown in Table 48. The August—hatched females produced more dozens of large eggs (509 dozen), medium eggs (69 dozen), small eggs (869 dozen), peewee eggs (140 dozen) and undergrade eggs (554 dozen) than the October—hatched females. On the other hand, the October-hatched females produced more doz- ens of jumbo eggs (192 dozen) and extra-large eggs (448 doz- en) than the August—hatched females. Season D (Auggst hatch) versus Season F (Decgmber hatch) The total egg production data per female hatched in August and December are presented in Table l. The data presented indicate the average numbers of eggs (hen-day basis) produced per female per two-week period. These data are graphically represented by Figures 9 and 11 and for comparative purposes by Figure 12. The August-hatched females laid at the rate of 5.4 eggs per bird during the initial record period (12). Whereas, the December-hatched females laid 9.0 eggs per bird during the same period. 88 The August-hatched females peaked in egg production per layer per period at 12.0 eggs, and the December-hatched females reached a peak egg production of 10.8 eggs per bird. Both the August-hatched and the December-hatched birds maintained a level of egg production of over 10 eggs per bird per period for seven two—week periods. The total egg production means were 8.15 and 8.01 eggs per bird hatched in August and December, respectively. Analysis of variance and Duncan's Multiple Range tests indicated the mean difference of 0.14 eggs per bird was not significant (Tables 5 and 6). The individual egg size distribution data of the August and December—hatched females are presented in Tables 28 through 54 and are graphically represented by Figures 15 through 18. Similarly, Tables 58 and 40 present the complete egg size distribution data of the August and December-hatched females and these data are graphically represented by Figures 22 and 24. A higher percentage of jumbo, extra-large and large eggs were laid by the August-hatched birds than by the 3December-hatched birds. The August-hatched females laid a higher percentage of medium eggs in the initial periods, 'but at one year of age the December-hatched females pro- duced a higher percentage of medium eggs. More small and Peewee eggs were laid earlier in the production periods by the August-hatched females than by the December-hatched 89 females. The Haugh unit scores of the eggs produced by the females in the extended lay periods are presented in Tables 41 and 42. These data are graphically represented by Figures 25 and 26. The average Haugh unit score of the eggs produced by the August-hatched females was 74.07 units. On the other hand, the December-hatched females produced eggs averaging 74.10 Haugh units during the ex- tended lay periods. The Shell thickness data of the eggs produced by the hens in the extended lay periods are presented in Tables 45 and 44 and are graphically represented by Figures 27 and 28. Season of egg production did not affect the shell thickness of the eggs produced by the August and December-hatched females shown in Table 45. The shell thickness of the eggs laid during the extended lay periods declined approximately 0.0005 of an inch. The detectable blood spot incidence data of the eggs produced by the August and December-hatched females are given in Tables 45, 46 and 47. Low percentages (1%) 0f blood spots were detected in most periods of lay. Iiowever, higher percentages (2—5%) of blood spots were .PIpduced by the August and December-hatched females during ‘the late summer, fall and early winter months shown in Table 45. age, 5!.J11I...Ilvtl"i «I: . : 90 Total egg production data, calculated in cumulative dozens of egg sizes per 1000 layers (hen-housed basis), are presented in Tables 48, 55 and 56. Tables 58-64, inclusive, present the cumulative individual egg weight distribution data per hatching season. The August-hatched females produced 2500 mere dozens of eggs than the December-hatched females. The August— hatched females produced more dozens of jumbo eggs (64 dozen), extra-large eggs (1171 dozen), large eggs (1505 dozen), medium eggs (1112 dozen) and undergrade eggs (68 dozen) than the December-hatched females. The December- hatched females produced more dozens of small eggs (556 dozen) and peewee eggs (864 dozen) than the August-hatched females. §g§son E (October hatch) versus Season F (Decggper hatch) The total egg production data per female hatched in October and December are presented in Table l. The data presented indicate the average numbers of eggs (hen- ciay basis) produced per female per two-week period. These (data are graphically represented by Figures 10 and 11 and for comparative purposes by Figure 12. The October—hatched females laid at the rate of 0.9 eggs per bird during the initial record period (12), and the December-hatched females laid 9.0 eggs per female during the same period. 91 The October-hatched females peaked in egg produc- tion per layer per period at 12.2 eggs, and the December— hatched females reached a peak egg production of 10.8 eggs per bird. The October-hatched females maintained a level of egg production of over 10 eggs per bird per period for 10 periods. On the other hand, the December-hatched females produced over 10 eggs per period for seven months. The total egg production means were 8.55 and 8.01 eggs per bird hatched in October and December. Analysis of variance and Duncan's Multiple Range tests indicated the mean difference of 0.52 eggs per bird was not significant (Tables 5 and 6). ‘ y The individual egg size distribution data of the October and December-hatched females are presented in Tables 28-54, inclusive, and are graphically represented by Figures 15—18, inclusive. Similarly, Tables 59 and 40 present the complete egg size distribution data of the October and December-hatched females, and these data are graphically portrayed by Figures 25 and 24. Higher percentages of jumbo, extra—large, large and Inedium eggs were laid by the October-hatched females than ‘by the December—hatched females. However, more small eggs ‘Were laid earlier in the record period by the October- hatched females than by the December-hatched females. Haugh unit scores of the eggs produced by the females in the extended lay periods are presented in Tables 41 and 42 92 and are graphically represented by Figures 25 and 26. The average Haugh unit score of the eggs produced by the October-hatched females was 74.75 units, while the December— hatched females produced eggs measuring an average of 74.10 Haugh units during the extended lay periods. The shell thickness data of the eggs produced by the hens in the extended lay periods are presented in Tables 45 and 44 and are graphically represented by Figures 27 and 28. Season of egg production did not affect the shell thickness of the eggs produced by the October and December—hatched females shown in Table 45. The shell thickness of the eggs laid during the extended lay periods declined approximately 0.0005 of an inch. The detectable blood spot incidence data of the eggs produced by the October and December-hatched females are given in Tables 45, 46 and 47. Low percentages (1%) of blood spots were detected in most periods of lay. How- ever, seasonally higher percentages (2-5%) of blood spots ‘Nere produced by the October and December-hatched females (luring the late summer, fall and early winter months. The total egg production data, calculated in cumu- 31ative dozens of egg sizes per 1000 layers (hen-housed ‘basis), are presented in Tables 48, 55 and 56. Tables 58 through 64 present the cumulative individual egg weight distribution data per hatching season. 95 The October-hatched females produced 1742 more dozens of eggs than the December-hatched females. The October-hatched females produced more dozens of jumbo (255 dozen), extra-large (1659 dozen), large (1505 dozen) and medium eggs (1151 dozen) than the December-hatched females. However, the December-hatched females produced more doZens of small (1421 dozen), peewee (1004 dozen) and undergrade eggs (185 dozen) than the October-hatched females. STRAIN II COMPARISONS Season B (April hatch) versus Season D (Auggst hatch) The total egg production data per female hatched in April and August are presented in Table 2. The data pre— sented indicate the average numbers of eggs (hen-day basis) produced per female per two—week period. The April-hatched females laid eggs at the rate of 2.5 eggs per bird during the initial record period (12). Whereas, the August-hatched females laid 5.8 eggs per fe- Inale during the same period. The April-hatched females IDeaked in egg production per layer per period at 11.5 eggs, and the August-hatched females reached this peak egg pro- duction of 12.2 eggs per bird. The April—hatched birds maintained a level of egg production of over 10 eggs per bird per period for three periods, while the August— hatched females produced at this level for 10 consecutive periods. The total egg production means were 7.88 and 9.68 eggs per bird, respectively. Analysis of variance and Duncan's Multiple Range tests indicated the mean differ- ence of 1.80 eggs per bird was highly significant (P <0.01, Tables 7 and 8). The total egg production data, calculated in cumu- lative dozens of sized eggs per 1000 layers (hen-housed basis), are presented in Tables 48, 51 and 54. Tables 58 through 64 present the cumulative individual egg weight distribution data per hatching season. The August—hatched females produced 5529 more dozens of eggs than the April-hatched females recorded in Table 1+8. The April-hatched females produced more dozens of jumbo (74 dozen) and extra-large eggs (666 dozen), but the August-hatched females excelled in the production of large (485 dozen), medium (2549 dozen), small (745 dozen), Jpeewee (89 dozen) and undergrade (505 dozen) eggs (Tables 51 and 54). ESeason B (April hatch) versus Season F (December hatch) The total egg production data per female hatched iin.April and December are presented in Table 2. The data IpIesented indicate the average numbers of eggs (hen-day ‘basis) produced per female per two-week period. ‘v! - 95 The April-hatched females laid eggs at the rate of 2.5 eggs per bird during the initial record period (12), while the December—hatched females laid 9.1 eggs per fe- male during the same period. The April-hatched females peaked in egg production per layer per period at 11.5 eggs and the December-hatched females reached a peak egg production of 10.8 eggs per bird. The April-hatched birds. maintained a level of egg production of over 10 eggs per bird per period for three periods while the December- hatched females produced at this level for only two periods. The total egg production means were 7.88 and 8.48 eggs per bird hatched in April and December, respectively. Analysis of variance and Duncan's Multiple Range tests in- dicated the mean difference of 0.60 eggs per bird was not significant (Tables 7 and 8). Total egg production data, calculated in cumulative dozens of sized eggs per 1000 layers (hen-housed basis), are presented in Tables 48, 51 and 57. Tables 58 through €¥+ present the cumulative individual egg weight distribu- 'tion data per hatching season. The December-hatched females produced 441 more (iozens of eggs than the April-hatched females (Table 48). {The April-hatched females produced more dozens of jumbo (140 dozen), extra-large (1482 dozen) and large (1486 dozen) eggs, but the December-hatched females produced 96 more dozens of medium (494 dozen), small (1910 dozen), peewee (1027 dozen) and undergrade (118 dozen) eggs. Season D (August hatch) versus Sggson F (Decggber hatch) The total egg production data per female hatched The data in August and December are presented in Table 2. presented indicate the average numbers of eggs (hen-day basis) produced per female per two-week period. The August-hatched females laid eggs at the rate of 35.8 eggs per bird during the initial record period (12), vvlule the December—hatched females laid 9.1 eggs per fe- .niale during the same period. The August-hatched females Jgreaked in egg production at 12.2 eggs per bird per period eaznd the December-hatched females reached a peak egg pro- Ciniction of 10.8 eggs per bird. The August—hatched birds IIlaaintained a level of egg production of over 10 eggs per ‘t>:ird per period for 10 consecutive periods and the December-hatched females produced at this rate for only 1ZVIO periods. The total egg production means were 9.68 and 8.48 Gaggs per bird hatched in August and December, respectively. lknalysis of variance and Duncan's Multiple Range tests in- ¢ was .m onswfim mcoflnom doapofidonm ®¢ 1} N14 0: mm mm #m mm om mm mm #N mm 0N ma ma #H NH _ a d _ _ e H _ _ _ _ 2 _ _ _ _ seeds _ Sam _ 3858 fl muesem _ $st _ Semi doe» :60 H wmm Ho numMmm_ m . I . m I . 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Hwy... :11. 21.1}. tfil..- .. . . . .. .1... 1... .. , \ .5 '44 I I. .wmmH .H nonemomn so Umnopmm mameHno mo nowpoSUOHm mmm h86IQmm mmwnm>< one .HH mnsmwm mUOHHmm GOHposdon um mm mm 0N mm #N mm mm HN ON OH wH NH OH mH #H MH NH __Pfigfi4_4______g nmsssm _ mqflnmm a; Hmque HHmm 4. Hosasm mqflnmm HOHposcon mmm no nommmm N m ..... l s . l m /.'1/. G00 /. . o 1 //u [I ’ I pill/c m I. ff 1 -m ./.\J|r./ ./. / m f/ \ ”Ir/cl! 4 0H HH ueH Jed 8883 go Jeqmnm e8eJeAv .4. . '.|.9vl - . ..--.....- AWN. . 109 .mebnmpaH thpnosHm pm Umnopwm mamxowno H qunpm Ho QOHposeonm mmm heelsom mmwnm>4 was .NH mnsmfim HmPQHe Hmpqfle Hmdea HHmm mdoHHmm QOHpodvon scenes .HO messes m scene; scenes Haas . Hams ueH Jed 3883 go qumnn e8easAv 110 Table 5. Analysis of Variance of Average Hen—day Egg Pro- duction for Chickens Hatched at Different Seasons. Strain I Source of F Variation D.F. S.S. M.S. Ratio Periods 4 425.6 106.400 Seasons 5 73.3 14.660 6.401 P x S 20 - 55.6 1.68 Error 180 425.7 2.55 New Error 200 457.5 2.29 Total 209 956.2 lSignificant P «.01. Table 6. The Results 0 Statistical Analyses of Egg Pro- duction Means for Chickens Hatched at Different Seasons. Strain I Production Means Ranked from Low to High 7.469 7.669 8.014 8.149 8.526 9.266 1Any two means not underscored by the same line are signifi- cantly different, and any two lots underscored by the same line are not significantly different. «a. 1.1-: . o —. o 111 Table 7. Analysis of Variance of Average Hen-day Egg Pro- duction for Chickens Hatched at Different Seasons. I Strain II ‘ Source of F Variation D.F. S.S. M.S. Ratio Periods 2 59.690 19.845 Seasons 35.480 17.740 7.101 P x S 4 4.210 1.052 Error 54 140.59 2.605 New Error 58 144.80 2.50 Total 62 219.97 1 Table 8. The Results 0 duction Means Seasons. Statistical Analyses of Egg Pro- for Chickens Hatched at Different Strain II Production Means Ranked from Low to High 7.88 8.48 9.68 1Any two means not underscored by the same line are signi- ficantly different, and any two lots underscored by the same line are not significantly different. 112 Table 9. Analysis of Variance of Average Hen-day Egg Pro- duction for Chickens Hatched at Different Seasons. Strain III Source of ' F Variation D.F. S.S. M.S. Ratio Periods . 2 45.71 22.86 Seasons 7 5 ~ 14.47 4.82 2.47 N.S. P x S 6 19.86 5.51 Error ‘ 60 117.00 1.95 Total . 71 197.04 Table 10. The Results 0 Statistical Analyses of Egg Pro- duction Means for Chickens Hatched at Different Seasons. Strain III Production Means Ranked from Low to High 9.51 9.51 10.11 10.28 L 1Any two means not underscored by the same line are signifi- cantly different, and any two lots underscored by the same line are not significantly different. 115 Table 11. Analysis of Variance of Average Hen-day Egg Pro- duction for Chickens Hatched at Different Sea- sons. Strain IV Source of F Variation D.F. S.S. M.S. Ratio Periods 5 48.74 20.140 Seasons 1 .55 .156 .085 N.S. P x S 5 2.42 .807 Error 48 79.50 1.652 New Error 51 81.72 1.602 Total 55 150-79 Table 12. The Results 0 Statistical Analyses of Egg Pro- duction Means for Chickens Hatched at Different Seasons. Strain IV Production Means Ranked from Low to High 8.545 8.496 IAny two means not underscored by the same line are signi- ficantly different, and any two lots underscored by the same line are not significantly different. 114 Table 15. The Average Heneday Egg Production of Strain I Females Hatched on April 1, 1958 and Housed in Different Pens. Age of Birds in Two—week Periods Prod. Approx. Pen1 Penl Penl Period Age of a b c Birds 14 28 6.5 5.9 7.6 15 ~ 50 7.8 8.6 9.5 16 52 10.9 9.7 10.5 17 54 11.2 9.9 11.0 18 56 11.0 9.5 10.1 19 58 10.6 9.2 10.2 20 40 10.4 8.8 10.5 21 42 10.2 8.6 9.8 22 44 9.7 8.5 9.8 25 46 9.6 8.5 9.1 24 48 9.1 8.7 9.2 25 50 8.8 8.5 8.8 26 52 8.2 8.5 8.9 27 54 8.4 8.9 9.0 28 56 8.1 8.5 8.4 29 58 8.4 8.5 8.5 50 60 8.6 7.9 8.1 51 62 7.7 7.9 8.0 52 64 6.7 7.1 7.4 55 66 6.7 7.1 7.0 54 68 5.8 6.8 6.7 55 70 6-5 ,7.5 6.7 56 72 6.4 7.1 6.7 57 74 6.4 7.0 7.1 .58 76 6.4 6.6 6.5 .59 78 6.4 6.8 6.1 4&0 80 6.5 6.9 6.5 1+1 82 6.1 6.1 6.2 £42 84 6.0 5.9 6.1 1+5 86 5.8 5.0 6.1 88 5.8 4.9 6.0 ‘+5 90 5.6 5.5 5-5 46 92 5.8 5.5 5.5 47 94 5.6 4.9 5.4 48 96 5.0 5.0 4.8 Egg Production Means 7.65 7.41 7.79 # See Appendix Table 7. 115 Table 14. Analysis of Variance of Average Hen-day Egg Pro- duction for Strain I Females Hatched on April 1, 1958 and Housed in Different Pens. M Source of F Variation D.F. S.S. M.S. Ratio Periods 4 229.568 57.590 Pens 2 ' 2.608 . 1.500 1.87 N.S. Interaction 8 6.118 .765 Error 90 61.871 .687 New Error 98 67.989 .694 Total 104 500.165 Table 15. The Results of Statistical Analyses of Egg Pro- duction Means for Strain I Females Hatched on April 1, 1958 and Housed in Different Pens. Production Means Ranked from Low to High 7.41 ' 7.69 7.79 Any two means not underscored by the same line are signi- ficantly different, and any two lots underscored by the same line are not significantly different. 116 Table 16. The Average Hen-day Egg Production of Strain I Females Hatched on June 1, 1958 and Housed in Different Pens. Age of Birds in Two-week Periods Prod. Approx. Penl Penl Period Age of d e Birds 15 50 11.4 11.2 16 52 12.4 12.0 17 54 11.9 11.4 18 56 11.5 11.0 19 58 11.5 10.5 20 40 11.0 9.9 21 42 10.5 9.5 22 44 10.0 9.5 25 46 10.0 9.5 24 48 9.9 9.5 25 50 9.6 9.2 26 52 9.2 8.6 27 54 9.1 8.9 28 56 8.5 8.2 29 58 8.0 7.9 50 60 7.4 7.4 51 62 7.2 7.4 52 64 7.0 7.1 55 66 7.1 7.1 54 68 6.9 6.7 55 ~70 7.0 6.6 56 72 7.1 6.7 57 74 7.2 6.6 58 76 7.0 6.5 59 78 6.7 6.3 40 80 6.2 5.9 41 82 6.4 5.8 42 84 5.5 5.6 45 86 5.6 5.2 44 88 5.9 5.1 45 90 5.8 5.0 46 92 5.9 4.7 47 94 5.8 4.7 48 96 5.8 4.4 49 98 5.8 5.2 Egg Production Means 8.09 7.56 I . _ See Appendix Table 7. 117 Table 17. Analysis of Variance of Average Hen—day Egg Pro- duction for Strain I Females Hatched on June 1, 1958 and Housed in Different Pens. Source of ' ' F Variation D.F. S.S. M.S. Ratio Periods 4 502.29 75.57 Pens 1 4.89 4.89 15.051 Interaction 4 2.17 .54 Error 60 18.69 .31 New Error 64 20.86 .525 Total 69 528.04 lSignificant P ..01. Table 18. The Results of Statistical Analyses of Egg Pro- duction Means1 for Strain I Females Hatched on June 1, 1958 and Housed in Different Pens. Production Means Ranked from Low to High 7-56 8.09 lhgy'two means not underscored by the same line are signi- IELcantly different, and any two lots underscored by the Sanw line are not significantly different. 118 Table 19. The Average Hen-day Egg Production of Strain I Females Hatched on October 1, 1958 and Housed in, Different Pens. Age of Birds in Two-week Periods Prod. Approx. Pen Pen Period Age of f g Birds 15 26 7.1 5.7 14 28 11.5 11.0 15 50 12.1 12.2 16 52 12.0 12.0 17 54 11.6 12.1 18 56 11.1 11.0 19 58 11.1 11.1 20 40 10.5 11.0 21 42 10.5 10.7 22 44 10.0 10.5 25 46 10.2 10.2 24 48 9.6 9.4 25 50 9.5 9.6 26 52 9.1 9.4 27 54 9.1 9.5 28 56 8.2 9.4 29 58 9.2 9.5 50 60 10.2 8.9 51 62 8.8 9.1 52 64 8.6 8.7 55 66 8.5 8.7 54 68 8.0 8.5 55 70 8.0 8.1 56 72 7.8 7.8 57 74 7-4 7-5 58 76 7.6 7.2 59 78 7.0 6.8 40 80 6.9 6.8 41 82 6.6 6.1 42 84 6.6 5.8 45 86 5-7 5.9 44 88 5.6 5.8 45 90 5-7 5.9 46 92 6.0 5.8 47 94 6.0 5.9 Egg Production Means 8.66 6.66 1 See Appendix Table 7. AIIIIIIIIIIIIII-——__________________________________________________ .._-IIII I 2115 '1. Vise; v . , . . u . . h“ ,. : .fhf .r! .... .M. .. o . . 119 Table 20. Analysis of Variance of Average Hen-day Egg Pro- duction for Strain I Females Hatched on October 1, 1958 and Housed in Different Pens. Source of F Variation D.F. S.S. M.S. Ratio Periods 4 212.95 55.25 Pens 1 0.001 O 0.0 N.S. Interaction -4 0.470 .12 .117 N.S. Error 60 61.780 1.05 Total 69 275.18 Table 21. The Results of Statistical Analyses of Egg Pro- duction Means for Strain 1 Females Hatched on October 1, 1958 and Housed in Different Pens. Production Ranked from Low to High 8.66 8.66 :yAny'two means not underscored by the same line are signi- .ficant1y different, and any two lots underscored by the seams line are not significantly different. fl . . . i. .1 .l. . tuft”... U. .. wmlwiL‘L Phn‘hi. .. 5.1!.» wilt It _., m... _. are.) .\_.d a...» e I 120 Table 22. The Average Hen-day Egg Production of Strain III Females Hatched on June 1, 1959 and Housed in Different Pens. Age of Birds in Two-week Periods Prod. Approx. Pen1 Penl Period Age of h i Birds 15 26 5.1 5.5 14 28 9.4 9.2 15 50 12.1 12.1 16 52 12.4 12.4 17 54 12.2 12.5 18 56 12.1 11.6 19 58 11.9 11.5 20 40 12.1 11.7 21 42 11.7 11.8 22 44 11.6 11.8 25 46 11.4 11.5 24 48 11.1 11.5 25 50 11.0 11.1 26 52 10.8 10.7 27 10.4 10.5 28 56 10.1 10.2 29 58 9.9 9.6 50 60 9.7 9.6 51 62 9.2 9.4 52 64 9.2 8.8 55 66 9.0 2.2 Egg Production Means 10.50 10.40 1See Appendix Table 7. . .. .. .. u: 0»: .4 I) l‘ . l v. .I V 4 . 1-1.! 0» I. . film" 0 . I! J '- . I n O . .. "v‘.l’x\‘ .l‘FI‘ Ix 121 Table 25. Analysis of Variance of Average Hen-day Egg Pro- duction for Strain III Females Hatched on June 1, 1959 and Housed in Different Pens. Source of F Variation D.F. S.S. M.S. Ratio Periods 2 25.12 12.56 Pens l 0.10 0.10 0.025 N.S. Interaction 2 0. 16 0.08 - Error 56 145.58 5.99 Total 41 168.96 Table 24. The Results of Statistical Analyses of Egg Pro- duction Means for Strain III Females Hatched on June 1, 1959 and Housed in Different Pens. Productions Means Ranked from Low to High 10.40 10.50 1 two means not underscored by the same line are signi- .ficantly different, and any two lots underscored by the :same line are not significantly different. I‘ll. ...-:u .1. r .... ”b.044lh—4...>w'v .. ......dv . ... . ... ...; .. ... . . . Om. . . l . ’5.» ...qu .. 4.....1 . ..\r r: - II III. .IIM....I.1. .H . .... ...!III“. II $1il.ill.. 1*“ III I . I Ill.llll III H II . u ‘lu ‘A . -..... IIII Lt I 1.1.1....” I... . _ l . Illlllll I II mlv. Ill .. . ..l). I l LII. D... I 122 Table 25. The Average Hen-day Egg Production of Strain IV Hatched on February 1, 1959 and Housed in Dif— ferent Pens. Age of Birds in Two-week Periods Prod. Approx. Penl Penl Period Age of j k Birds 11 22 1.5 1.1 12 24 5.0 4.5 15 26 8.4 7.9 14 28 9.8 9.7 15 50 10.1 9.7 16 52 10.5 10.1 17 54 10.5 10.2 18 56 10.2 10.0 19 58 10.2 9.6 20 40 10.0 8.9 21 42 9.5 8.6 22 44 9.7 8.6 25 46 9.8 7.9 24 48 9.7 7.9 25 50 9.2 7.7 26 52 8.2 7.7 27 54 8.0 7.2 28 56 7.7 7.5 29 58 7.9 7.8 50 60 8.1 7.6 51 62 8.2 7.8 52 64 8.5 7.7 55 66 8.4 7.6 54 68 8.1 7.6 55 70 7.9 7.5 56 72 7.5 7.2 57 74 7.4 6.9 58 76 7.2 6.5 59 78 7.1 6.4 40 80 6.2 6.0 Egg Production Means 8.547 7.707 1See Appendix Table 7. Table 26. 125 Analysis of Variance of Average Hen-day Egg Pro- duction for Strain IV Females Hatched on February 1, 1959 and Housed in Different Pens. Source of F Varfi.ation D.F. S.S. M.S. Ratio Periods 2 11.45 5.71 Pens 1 6.18 6.18 1.855 N.S. Interaction 2 0.66 0.55 Error 54 181.81 5.567 T0132a1 59 200.08 5Pal>le 27. The Results of Statistical Analyses of Egg Pro- duction Means for Strain IV Females Hatched on February 1, 1959 and Housed in Different Pens. Production Means Ranked from Low to High 7.707 8.347 .Aer two means not underscored by the same line are signi- iiicantly different, and any two lots underscored by the ESame line are not significantly different. 124 Table 28. The Percentage of Jumbo Eggs Produced by Females Hatched at Different Seasons of the Year. Pe- Seasons Pe- Seasons riod A B C D E F riod A B C D E F 11 l 5 59 5 2 5 5 4 2 12 2 3 2 3 40 3 3 2 2 4 1 13 1 2 2 1 3 2 41 3 4 3 4 4 2 14 1 2 1 1 2 1 42 4 6 4 4 4 1 15 1 1 1 1 2 1 43 5 6 5 4 4 1 16 1 1 1 44 6 5 5 5 4 3 17 1 1 45 7 6 5 5 5 4 18 1 46 11 7 6 3 5 6 19 1 47 12 10 6 3 5 6 20 48 14 9 6 3 6 2 21 49 12 6 4 3 b 22 50 l5 9 5 5 9 25 51 12 9 4 3 11 24 52 15 9 4 3 11 25 55 14 6 5 6 9 26 54 11 5 4 6 27 55 11 6 5 8 28 56 12 6 5 7 29 1 1 1 2 1 57 15 6 2 30 l 2 58 12 5 5 31 2 1 1 l 59 12 4 6 52 1 1 1 1 6o 11 5 7 33 l 1 2 1 1 61 10 6 5 34 2 1 1 1 5 1 62 9 8 35 3 1 1 1 3 65 8 9 36 3 1 2 2 5 64 7 8 37 315251 65 67 58 5 2 4 5 5 2 1 ' 8- 0. June 1 1958- A. Februar 1 1958- B. April 1, 195 a 9 1 L D. August 1, 1958; E. October 1, 1958; F- December 1. 1953- .1134. I. p! #5.} lullllul I ....l . . . 125 .Hmow on» Ho muommom pnonommwn pm donopmm monSom hp 6005609m mmwm onssw mo ommDQooHom one 00 so No 00 mm mm #m mm om m¢ ode: m¢ or mm scram seems scram roses scrum sopcm mama .m sossooon mama a sopopoo mmma .H enemas wmma .H cuss mmefl .H Hands mmma H sonogram QZMGMH mUOHnom noeposoonm OIOIO lollololl .MH cusses OH mH ON paonpomg S883 oqmnp quasieg 126 Table 29. The Percentage of Extra-large Eggs Produced by Females Hatched at Different Seasons of the Year. Pe— Seasons Pe- Seasons rioéi A B C D E F riod A B C D E F 11 39 3O 25 50 28 32 19 12 4o 32 26 33 26 34 19 15 41 33 32 35 28 36 20 141 42 56 54 55 29 55 21 15 45 38 54 55 51 34 25 16 1 44 41 34 31 52 55 25 17 45 42 55 29 52 55 29 18 2 1 46 41 55 29 5O 56 55 199 2 1 1 1 47 42 54 50 29 55 57 2o 2 2 1 1 1 48 42 34 30 28 39 21. 2 3 2 2 1 49 45 51 31 30 55 22 4 4 3 3 2 2 50 46 32 52 50 58 23 7 7 4 5 3 5 51 45 51 51 50 59 21+ 10 9 5 3 4 5 52 40 32 30 3o 42 25 13 11 6 5 5 6 55 4O 54 29 52 54 26 14 12 8 6 ' 7 7 58 55 27 55 27 16 15 9 6 ll 8 55 57 55 29 55 28 19 14 8 6 15 1 56 57 55 29 55 29 22 14 7 8 18 13 57 37 33 32 50 25 16 8 12 21 13 58 42 34 33 It. February 1, 1958; B. April 1, 1958; C. June 1, 1958; I). August 1, 1958; E. October 1, 1958; F. December 1, 1958. 127 .Hmmw mg» no mqomwom pnmanMHn pw donopwm moawamm an voofiooum mwwm ownmqlmnpxm mo wwaQmoHom one .¢H onswfim chHHmm qoaposvonm OH ma om mm om mm O# m: on peonpoag 8283 aSJeq-eaqxg queoaea o .. 1‘ ... . . 4 I .4 1 I o. 4‘ a J.‘o.; . . . Q 6 . a? . " .y;..-p‘ SOII’: “'1. I .. . A , L \Il“ I H‘ . "|| 1‘ 11 {I 05.104110» . 3V. (n. .ilnx'NII . ‘AWIAV 30. February 1, 1958; B. April 1, 1958; C. June 1, 1958- . August 1, 1958; E. October 1, 1958; F. December 1, The Percentage of Large Eggs Produced by Females Hatched at Different Seasons 3.112 129 £8.83 3 pm eonopmm .HMmM on» no mqomwom mmamaom ha ooosdonm mmmm wwnmq mo oMMononom one .mH onsmwm mvoanmm nowpodvoym #w om ommnmw #0 ow mm mm m¢i~o¢ mmmmwm #N OH ma ON mm om mm 01» m¢ on R peonpoaa $883 98191 queoaeg at...” .....J .— er-I‘A r.. . . .0. .4 . . .U . i .1.‘ .rl . . . 1 3.. .2. ... \ww r1? 1.9.. I . . r-;.. . ~91.- F . . . . ..11......».s...& .. I 1.1.! 9.1.. ....I. . . . ...... . . L .f 1hr ...... 4 . PW: ...V. T . . I)- ..- .1 t A.I..11.1..v :|“ll~,. 1'9.‘ HQ'H.’ . 1 I . . .t. . u - ... 17.11". .3114... 1.11.0...rlwl “.... :wa 1.4.. 1‘ 150 Table 51. The Percentage of Medium Egg? Produced by Females Hatched at Different Seasons of the Year. Pe— Seasons Pe- Seasons riod. A B C D E F riod A‘ B C D E F 4 59 14 21 16 14 22 5 4 4O 15 16 15 15 10 25 15 6 41 l5 l4 l5 8 10 25 5O 14 42 ll 12 12 9 11 22 45 24 45 10 15 14 9 12 22 64 56 44 7 14 15 ll 15 19 7O 49 45 6 15 12 11 15 15 7O 61 46 5 15 10 12 15 12 68 64 47 4 15 10 14 1 9 67 65 48 4 15 11 15 15 9 65 65 49 4 11 12 15 12 62 65 5O 5 9 15 16 9 57 61 51 5 l6 l7 7 54 52 6 10 17 15 6 52 51 55 7 12 18 10 6 46 47 8 18 9 58 45 55 6 15 18 8 28 58 56 5 14 19 9 25 55 57 4 l4 17 22 55 58 5 l5 15 2O 5O 59 5 15 12 18 28 6O 6 16 11 16 21 61 7 16 11 15 15 62 8 14 17 19 65 8 12 15 2O 64 8 11 15 2O 65 8 11 9 21 11. February 1, 1958; I). August 1, 1958; E. B. April 1, 1958; C. June 1, 1958; October 1, 1958; F. December 1, 1958. 151 .HMoM on» no mqomwom pnohommfln pm Umnopmm moamamm hp couscohm mmmm 352605 mo mwmpnoonom one mUOHHOM fiOfiPOfiUOE .62 onsmfim peonpolg $883 mnrpaw queozeg 152 Table 52. The Percentage of Small Eggs Produced by Females Hatched at Different Seasons1 of the Year. Pe— Seasons Pe- Seasons riod A B C D E F riod A B C D E F ll 51 11 59 l 1 l 12 54 9 49 5O 5O 4O 1 1 1 15 57 52 62 65 55 5O 41 1 l 14 48 6O 56 6O 55 6O 42 l 1 15 56 55 44 52 42 6O 45 16 28 42 52 42 24 55 44 1 17 2O 55 52 52 16 42 45 1 18 17 24 2O 51 12 5O 46 19 12 17 16 15 9 25 47 2O 10 11 ll 11 8 25 48 21 7 9 8 8 7 2O 49 22 6 7 6 5 5 12 50 l 25 5 5 5 5 4 5 51 24 2 4 4 4 4 5 52 l 25 l 5 5 4 4 2 55 26 l 5 2 5 4 2 54 27 l 2 2 5 2 2 55 1 1 28 1 2 5 5 1 l 56 29 l 4 5 1 57 5O 1 1 5 2 58 1 51 1 2 1 2 59 52 l -2 l 1 6O 55 2 2 61 54 2 2 62 55 1 1 l 65 1 56 l 1 64 57 1 65 1 58 1 1 1 11. February 1, 1958; B. April 1, 1958; 0. June 1, 1958; D. August 1, 1958; E. October 1, 1958; F. December 1, 1958. .... .P. .......I. II I .1. . (£130.. . 7. 155 .Hmmw can no mqomwom unonmwmfln pm donopwm mmHmamm hp doonUonm mwmm HHmam mo oOdpnoonm one .mH mnsmflm mm meHHom OH mH ON mm on mm O¢ m4 om mm 0m peonpoaa 8223 Items quaoaaa . -0 ‘1 l.. --lnt. . 1'... 11"- f.-l. - O . D’O‘I. 154 Table 55. The Percentage of Peewee Eggs Produced by Fe- males Hatched at Different Seasons1 of the Year. fiEeTigfiggk Hatching Season Intervals A B C D E F 11 58 68 12 27 52 42 4O 56 15 9 24 52 7 28 54 14 5 l5 l4 6 10 l9 15 l 7 5 5 5 10 16 .1 5 2 6 l7 5 l l 5 18 2 l 19 1 2O 1 1A. February 1, 1958; B. April 1, 1958; C. June 1, 1958; D. August 1, 1958; E. October 1, 1958; F. December 1, 1958. .Hmmw mnp Ho mnommmm pnonoHHHn pm dmgopwm monaom hp Umoddonm mmwm cosmom Ho omwpnoonom one .wH ondmflm wGOHHom QOHposUOHm 638m 83 .m 63888 ...Iolo 638m mama H .3638 I I E nopwm mm? .H 6263 l-.-.- 1 no»... mm? .H 236 - - - - gopmm wmmfl 0H HHand o o n a o 0 serum mm? .H 8865206 II nzmwmn peonpozd $333 sensed queomea . .I 1 1.- ...\l 0I.I.l.4t. ..lll.4. ... DO- 1»- 1 . . . . . . w..n._fl.r...-1L.. 5. ., . : . n. . . .. , q. .14”. . . , r’kl .1.le.lhlvw..l1.-t‘.2y$|flrrfl. . I .aua . . i I . ....l. . .1 I -.-! .1. .It. HM...“ .c..,..... .> .. ,. ..l. l.. . i. 156 Table 54. The Percentage of Undergrade Eggs Produced by Females Hatched at Different Seasons1 of the ‘ Year. Pe- Seasons Pe— Seasons riod A B C D E F riod A B C D E F 11 59 8 10 6 11 9 7 12 2 2 2 6 4O 8 10 6 12 7 7 15 2 2 5 2 2 7 41 9 10 7 15 7 8 l4 2 2 2 5 5 5 42 8 ll 8 l2 8 9 15 1 2 2 2 4 4 45 8 10 9 10 7 10 16 2 2 2 2 4 4 44 9 10 9 9 7 ll 17 2 2 2 2 4 4 45 9 9 10 9 7 10 18 2 2 2 2 2 4 46 10 9 10 9 7 9 19 2 2 2 5 2 5 47 1 10 10 9 9 8 2O 2 2 2 4 2 5 48 11 10 8 8 10 7 21 l 2 2 4 2 5 49 ll 8 6 8 10 22 2 2 2 4 5 5 5O 9 12 6 7 9 25 5 5 2 5 4 5 51 9 11 6 8 9 24 5 - 4 5 4 4 6 52 9 9 8 8 8 25 5 5 4 6 4 7 55 ll 8 8 10 8 26 5 5 4 5 5 6 54 12 7 8 11 27 5 5 4 7 . 5 6 55 15 7 8 10 28 5 5 4 7 5 6 56 12 7 8 9 29 5 6 4 8 5 7 57 10 7 8 5O 5 6 5 7 6 8 58 8 7 10 51 4 6 6 8 6 9 59 9 7 lO 52 6 6 8 7 7 10 6O 9 8 10 55 6 6 8 8 7 10 61 9 10 8 54 6 7 9 8 8 9 62 8 10 55 6 8 8 9 9 8 65 8 9 56 7 10 8 9 9 8 ,64 8 9 57 8 10 7 10 11 8 65 8 9 58 8 11 7 11 10 7 lA. February 1, 1958; B. April 1, 1958; C. June 1, 1958; D. August 1, 1958; E. October 1, 1958; F. December 1, 1958. 157 Table 35. The Distribution, in Percentage,1 of Egg Heights Recorded in Two-week Intervals for Females Hatched on February 1, 1958. Pe- Egg Weights2 Pe- Egg Weights2 riod J XL L M 8 PH UG riod J XL L M S PW UG 11 l 7 51 58 2 59 5 5O 44 14 12 2 15 54 27 2 4O 5 52 45 15 8 15 1 1 50 57 9 2 41 5 55 41 15 9 14 l 2 45 48 5 2 42 4 56 40 ll 8 15 l 4 56 56 l l 45 5 58 59 10 8 16 l 7 62 28 1 2 44 6 41 57 7 9 17 11 66 2O 2 45 7 42 55 6 9 18 2 15 67 17 2 46 ll 41 52 5 10 19 2 17 67 12 2 47 12 42 51 4 10 2O 2 21 65 10 2 48 14 42 52 4 ll 21 2 25 65 7 l 49 12 45 27 4 ll 22 4 27 6O 6 2 5O 15 46 27 5 9 25 7 54 55 5 5 51 12 45 27 5 9 24 10 4O 45 2 5 52 15 4O 29 6 9 25 15 47 55 1 5 55 14 4O 28 7 ll 26 14 47 54 l 5 ll 58 51 8 12 27 16 49 51 1 5 55 ll 57 55 6 15 28 19 49 28 l 5 56 12 57 54 5 12 29 l 22 5O 24 5 57 15 57 54 4 10 5O 25 49 21 1 5 58 12 42 55 5 8 51 2 26 49 2O 4 59 12 41 54 5 9 52 1 27 48 17 6 6O 11 42 55 6 9 55 1 27 47 17 6 61 10 59 55 7 9 54 2 27 47 16 6 62 9 58 55 8 8 55 5 28 47 16 6 65 8 56 59 8 8 56 5 28 47 15 7 64 7 58 58 8 8 57 5 29 45 15 8 65 6 58 56 8 8 58 5 29 45 l5 8 lPercentage calculated as a moving average of three two-week periods, Haugh (1945). 2J-Jumbo; XL-Extra Large; L—Large; M-Medium; S-Small; PW—PeeWee; UG-Under Grade. .mmmH .H hnwsnpom no UmAODmm mmHmaom mom mHm>Hmp IqH Mooslose qH wodnoomm mpnmwoz mwm Ho.mm8pqoonmm nH .nOHpanngmHQ one .mH onstm mUOHHonH flounpoddohm mmHmmHsmfiomHoflmfiwOHgH 00H mm mm mm 4w om mm. mm. mm +8 ow mm mm @113 0+. mm mm mm 4m om OU\ OU\ (UNI-1H JO queoaeg 158 QZHOQH Tm_ quHmm _ HmquB _ Hme _ Hmaadm _ qunmm _ Honda; _ Hme _ noaadm 44 noHpoduonm mmm mo nommmm 159 Table 56. The Distribution, in Percentage,1 of Egg Weights Recorded in Two-week Intervals for Females Hatched on April 1, 1958. Pe- Egg .‘Ieights2 Pe- Egg Weights2 riod J XL L M S PW UG riod J XL L M S PH UG ll 59 2 25 42 21 l 10 12 5 6 59 52 4O 5 26 41 16 l 10 15 2 ll 62, 24 l 41 4 52 59 14 l 10 14 2 25 6O 15 2 42 6 54 58 12 1 ll 15 l 2 56 55 7 2 45 6 54 58 15 10 16 l 5 48 42 5 2 44 5 54 57 14 10 17 l 6 56 55 5 2 45 6 55 57 15 l 9 18 l 1 ll 61 24 2 2 46 7 55 55 l5 l9 1 l 16 61 17 l 2 47 10 54 55 15 10 2O 2 25 59 ll 1 2 48 9 54 55 15 10 21 5 27 58 9 2 49 6 51 59 ll 8 22 4 52 54 7 2 5O 9 52 58 9 l 12 25 7 55 49 5 5 51 9 51 4O 11 24 9 59 45 4 4 52 9 52 59 10 9 25 ll 40 41 5 5 55 6 54 4O 12 8 26 12 45 57 5 5 54 5 55 59 15 7 27 15 45 54 2 5 55 6 55 59 15 l 7 28 14 47 52 2 5 56 6 55 59 14 7 29 1 14 47 5O 1 6 57 6 55 59 14 7 5O 1 16 47 29 1 6 58 5 54 4O 15 7 51 1 16 48 29 l 6 59 4 55 58 l5 7 52 1 16 47 29 l 6 6O 5 54 57 16 8 55 l 17 47 28 2 6 61 6 55 55 16 10 54 1 17 46 26 2 7 62 8 51 57 14 l 10 55 l 21 45 25 l 8 65 9 55 56 12 l 9 56 1 22 45 24 l 10 64 8 56 56 ll 9 57 l 21 42 24 l 10 65 7 58 55 ll 1 9 58 2 22 41 24 l ‘ 11 If Percentage calculated as a moving average of three two- week periods, Haugh (1945). 2J—Jumbo; XL—Extra Large; L-Large; 111-Medium; S—Small; PW—PeeWee; UG-Under Grade. 140 .wmmH .H HHHmd no canopmm monEom now mHm>Hoan MooBIoBe qH wodhooom mpnmwoa wwm Ho .omprmoHom 6H .qOHpanHpmHn one mdoanmm defipouoohm wNHsmHONHdeNHHOOH¢OHOOH®® mm mm #m ow on NB mm.¢mom mm mm m4 4% 04 mm mm mm #N QZHOmH .om enswfim in o uxcann o uxcaun o mxcatn o .o o ux.n 4 d-rn xxcu m r4.4 uorqonpoag 983 go queoaaa _ Hmaafim — menmm _ Hopnfia _ Hme _ Hoaasm _ mnHHmw _ HoquB _ Hme _adm. qOHposuon wmm no nonwom 141 Table 57. The Distribution, in Percentage,1 of Egg Weights Recorded in Two-week Intervals for Females Hatched on June 1, 1958. Pe- Egg Weights2 Pe- Egg Weights2 riod J XL L. M 8 PW UG riod J XL L M 8 PH UG 11 39 3 3o 44 16 1 6 12 2 49 42 2 4o 2 35 42 15 1 6 13 2 11 52 32 3 41 5 55 4o 13 1 7 14 1 26 56 14 2 42 4 35 39 12 1 8 15 1 4 44 5 2 43 5 33 38 14 9 16 1 5 58 32 2 2 44 5 31 41 13 9 17 7 62 29 1 2 45 5 29 42 12 10 18 10 66 2o 1 2 46 6 29 45 10 10 19 1 15 65 16 2 47 6 5o 44 10 10 2o 1 ‘21 64 11 2 48 6 5o 45 11 8 .21 2 26 61 8 2 49 4 31 45 12 6 22 3 3o 57 6 2 5o 5 32 44 13 6 23 4 34 54 3 2 51 4 31 43 16 6 24 5 37 50 4 3 52 4 3o 42 17 1 8 25 6 39 48 3 4 55 5 29 42 18 8 26 8 41 44 2 4 54 4 27 42 18 8 27 9 43 42 2 4 55 5 29 41 18 8 28 8 42 43 3 4 56 3 29 4o 19 8 29 1 7 42 42 4 4 57 5 52 4o 17 8 5O 8 45 4O 5 5 58 5 55 55 15 l 10 51 12 :45 35 2 6 59 6 35 37 12 10 52 14 45 32 2 8 6O 7 37 35 11 10 .53 15 45 3o 2 8 61 5 36 59 11 8 .54- 1 17 44 28 2 9 62 55 1 21 46 23 1 8 63 36 2 25 46 18 1 8 64 57 3 26 46 17 7 65 38 4 26 45 17 1 7 ‘ Percentage calculated as a moving average of three two-week Periods , Haugh (1945) . 22 iT-Jumbo; XL—Extra Large; L-Large; M-Medium; S—Small; PHI-Peewee; UG-Under Grade. 142 .wmmH .H mafia no conopmm mmHmamm How me>Hoqu #0031033 nH covnooom mpAMHoa wwm mo .owmpnoonom qH .HOdepHHpmHQ baa .Hm onswwm mdoanom QOHposconm ¢NHONHOHHNHHOOH¢OHOOH mm mm mm #m ow mm. mm. mm #0 ow mm mm 9.130.: mm mm mm #m 2 H6355 # quHmmL song”; _ HHmm — Roam —mnH.Hmm _ .18qu; _ HHwfl 60Hposdonm wwm no nomwmm uorqonpoq 383 JO 211190.195 145 Table 58. The Distribution, in Percentage,lof Egg Weights Recorded in Two-week Intervals for Females Hatched on August 1, 1958. Pe— Egg Weights2 Pe- Egg Weights2 riod J XL L M 8 PW UG riod J L M 8 PW UG 11 59 5 28 43 14 11 12 4o 2 26 46 13 12 13 25 65 7 3 41 4 28 47 8 13 14 1 1 29 6o 6 3 42 4 29 45 9 12 15 1 1 4o 52 5 2 45. 4 31 45 10 16 2 50 42 2 2 44 5 52 45 11 9 17 4 59 33 1 2 45 5 52 44 11 9 18 8 66 31 2 46 3 3o 44 12 9 19 l5 67 l5 5 1+7 5 29 45 l4 9 2o 1 18 66 11 4 48 3 28 46 15 8 21 2 23 61 8 4 49 5 5o 45 15 8 22 3 28 59 5 4 50 5 5o 43 16 7 25 5 29 57 5 5 51 5 50 42 l 8 24 3 31 56 4 4 52 3 3o 42 15 8 25 5 33 53 4 6 53 6 32 41 10 10 26 6 57 48 5 5 54 6 35 38 9 11 27 6 57 47 5 7 55 8 55 57 8 1 10 28 6 57 47 5 7 56 7 55 58 9 9 29 8 4o 42 3 8 57 3o 12 45 34 2 7 58 51 18 48 25 1 8 59 52 1 21 48 21 1 7 6o 35 2 25 47 2o 8 61 54 1 25 47 18 8 62 .35 1 27 46 17 1 9 63 36 2 29 45 15 9 64 37 2 3o 44 14 10 65 38 3 29 41 15 11 Percentage calculated as -a moving average of three two— Week periods, Haugh (1945). 22 {Te-Jumbo; XL-Extra Large; L—Large; M-Medium; S—Small; Pu‘J-Peewee; UG—Under Grade. .mmmH .H pmsws¢ no emnopmm mewsmm now mebnman MooBIoBa qH Umvnooom mpanoe mmm Ho .mMMpdooHom qH .qOHpanHpmHn one .mm ondwfim mdoHHom QOHposdohm mm #m mm on m4 014 .3 N4 04 mm mmemmm Om mm mm¢m mm ome OH 4H NH .. o m ...... mH a u ON 4 mm m. 0m 3 m ...... mmwm mm mosoom o¢.m mm HHwam II m4 W m m ademS I.-. mwwm ownmg I I on m .82 mm m oman mnpxm .... om mwmm onadh mm szwmq on possum QHH m _ HoanB _ Hme noaaam _mafinmm _ Hmquwxg QOHposwonm mmm Ho acumen 145 Table 59. The Distribution, in PercentageP-or Egg Weights Recorded in Two-week Intervals for Females Hatched on October 1, 1958. Age Egg Weights2 Age Egg Weights2 of J XL L M 8 PW UG of J XL L M 8 PW UG Birds Birds 22 78 4 32 46 9 24 5 50 4o 2 8O 4 34 45 1o 7 26 5 13 53 28 2 82 4 56 42 10 7 28 2 3o 55 10 3 84 4 35 42 11 8 3o 2 2 45 42 4 86 4 34 41 12 7 32 1 4 64 24 4 88 4 33 42 13 1 7 34 1 8 7o 16 4 9o 5 35 4o 13 7 56 15 70 12 2 92 5 56 59 15 7 38 1 18 68 9 2 94 5 55 58 13 9 4o 1 2o 67 8 2 96 6 34 38 13 10 42 1 24 65 7 2 98 6 35 37 12 10 44 2 28 62 5 5 100 9 38 34 9 9 45 5 52 57 4 4 102 ll 59 54 7 9 48 4 33 54 4 1+ 114 11 42 35 6 8 5o 5 34 52 4 4 106 9 43 34 6 8 52 7 38 46 4 '5 11 44 38 2 5 56 15 5o 28 1 5 58 2 18 49 25 5 60 2 21 49 22 6 62 1 24 49 2o 6 64 1 26 49 18 7 66 1 5o 46 16 7 68 3 34 41 15 8 7O 5 55 58 l7 9 72 5 55 59 15 9 74+ 3 3o 43 13 11 '76 3 31 46 9 1o \ Percentage calculated as a moving average of three two- Week periods, Haugh (1945). 22 CF—Jumbo; XL-Extra Large; L—Large; M-Medium; S-Small; PEN-Peewee; UG-Under Grade. 6 4 l mmwm odmnwnoUQDIlNllN mwmm omsoomnlollo mwmm HHmam II II mwmm azHuos I.I.I Emma owan I I I wwwfi ownwn unpxfi ..... mwmm opafib IIIII QZHOMH .wmmH .H Hmpopoo no donopwm monamm non mHmbnoan MwoBIoBa aw dovnooom mpanoe mmm mo .owmuqmonom QH .qOHpsnflnpmHn 058 .mm ondem meownom QOHposwonm ..qm Nm Om N.» 0.1 .3 N# O¢Om mm 1.4m NM Om ON ON #N NN ON OH OH #H NH —& Hmaadm ._ mqflnmm a Hopnfle _ Hme mewaasm — wanmm _ .34 QOHpoddonm mmfi mo nonwom uorqonpoag 883 go queoaeg 147 Table 40. The Distribution, in Percentage,1 of Egg Weights Recorded in Two-week Intervals for Females Hatched on December 1, 1958 Age Age of J XL L M S PW UG of J XL L M S PW UG Birds Birds 22 5 4 18 68 6 78 2 19 49 22 l 7 24 5 2 4 5O 56 6 8O 1 19 48 25 l 7 26 2 6 5O 54 7 82 2 2O 48 25 8 28 l 14 6O 19 5 84 l 21 46 22 9 5O 1 l 24 6O 10 4 86 1 25 45 22 10 52 56 55 6 4 88 5 25 41 19 ll 54 l 49 42 5 4 9O 4 29 41 15 10 56 4 61 5O 4 92 6 55 41 12 9 58 5 64 25 5 94 6 57 41 8 4O 6 65 25 5 96 2 59 4O 9 7 42 9 65 2O 5 44 2 17 65 12 5 46 5 25 61 5 5 48 5 51 54 5 6 50 6 55 51 2 7 52 7 58 47 2 6 54 8 41 45 2 6 56 11 45 58 1 6 58 l 15 46 55 l 7 6O 15 45 55 8 62 l 12 47 5O 2 9 64 12 48 28 1 10 66 1 15 54 21 10 68 1 15 56 15 9 7O 18 55 19 8 72 2O 51 2O 8 74- 1 2O 5O 2O 8 76 2 19 5O 21 l 7 IPGBrcentage calculated as a moving average of three two- Week periods, Haugh (1945). 22 {T-Jumbo; XL-Extra Large; L—Large; m-Medium; S—Small; IPEI-Peewee; UG-Under Grade. 8 4 1 mwmm muwmmhocnb IINIIN mmwm mmsmmm Ilollo wwwm HHmam II II wwwm adHuos .I.I.I mmmm owan I I I _mwwm mmnwn wnpxm ...... mmmm 096:6 szwmm mdofinom QOHpoddon .wmmH .H Honaoomn no omnopmm mmHmamm How mHmbnoqu MooBIosB qH dovnooom mpamfloz mmm Ho .mmmuqbonom 6H .qOdeDHHpmHQ one __ Hmaasm _ wnfinmm _ Hoque _ Hme ..Hmaadm qOHposuon mmm mo nomwmm _wanmm_ .sm 3&8 3 ma om. mm on mm 0.. me on mm om mm on uorqonpomg 883 JO queolea 149 Table 41. The Haugh Unit Scores1 for Eggs Laid by Chickens Hatched at Different Seasons of the Year. (By Age of Birds). Hatching Season Period A B C D E F 24 79 25 81 26 81 27 80 28 79 29 77 74 50 78 72 51 79 75 52 76 80 72 55 78 81 75 54 79 75 76 55 78 72 74 56 77 75 70 57 77 71 76 75 58 79 71 75 76 59 80 75 74 7o 40 79 76 77 65 41 79 78 75 74 66 42 81 71 73 72 72 43 81 74 71 75 77 44 79 75 68 69 72 45 78 74 7O 65 70 46 75 75 74 69 65 75 47 75 75 75 65 75 75 48 75 75 77 66 79 77 49 77 71 75 68 76 75 50 77 76 71 74 75 71 51 72 78 69 8O 75 74 ,52 71 81 68 76 74 76 55 75 80 71 74 74 75 78 76 72 76 72 555 75 75 75 75 75 £56 76 74 81 76 78 557 80 67 71 76 80 558 77 66 71 75 76 539 76 75 75 77 €50 67 82 75 79 €51 64 77 76 78 €32 65 75 74 €55 64 80 75 €54 74 80 78 €55 8O 79 80 J¥xr€56 75 77 r~11‘W'o two-week moving averages, Waugh (1945). 150 .AmdnHm .Ho 09H 65 880% 05. .Ho mnomw0m pnmhmmmHn 80 608085 0413885 .3 chH mmmm How m0noom p.25 demm 088 .mm 0.5...me muoHn0m 483086on #0 mm 00 mm mm in mm on 94 m4 .1. N14 04 mm mm #m mm 0m .5304 . mm 8083. mmmH H H0pa0omn IoIo 1.336 < 638m 83 . Hnepopeo I I gopmm wmmH ..H.H pmsmsa .I.I.I . om gopmm wmmH H 086 I I I HHOPMHH wmwfla H HflHnH4 o o o e b o H 30m ...mme H 88390.06 . mm m ... 8 . ... qzmwMH I\.. \V./ ./ B m. M .. . o 4 .. \IJ ... .I/\\ \7\I1IIyA..../. .. /\/p/./ / .I/.\0VA Nb W... .. . .. o \l < \\I p ... ..\..\. I. 'l/ f o e. :0 S \ I/\\\ \ .. §/\ fl 45.1 (< . mm. \\ an. - >o/ .. .. .7“ /.A. f \ ...: ...... < ...... ..... I\I.I /\\ . 0w . mm 151 Table 42. The Haugh Unit Scores1 for Eggs Laid by Chickens Hatched at Different Seasons of the Year. (By Similar Date of Sample). Hatching Season Sample A B C D E F 1 75 79 77 76 77 79 2 75 81 79 78 78 81 5 75 81 80 79 79 81 4 77 79 79 78 8O 80 5 77 78 78 77 81 79 6 72 75 71' 71 75 74 7 71 75 74 71 72 72 8 75 75 75 75 75 75 9 78 71 74 76 76 72 10 75 76 7“L 75 75 75 11 76 78 75 75 74 76 12 80 81 77 71 77 74 15 77 80 75 68 74 7O 14 76 76 71 70 72 75 15 67 75 69 69 75 76 16 64 74 68 65 69 7O 17 65 67 71 66 65 65 18 64 66 72 68 65 66 19 74 75 75 74 75 72 2O 80 82 81 80 79 77 21 77 71 76 76 72 22 75 71 74 75 7O 25 80 75 76 75 75 24 80 75 75 74 75 25 79 76 76 74 77 26 75 74 76 72 75 27 75 75 75 71 28 78 77 78 74 29 80 79 80 76 .50 77 78 76 75 Il‘rtarage 75.55 76.46 74.77 74.07 74.75 74.10 CDVvo two—week moving averages, Waugh (1945). .Aonamm mo mpmm HmHHaHm hmv .Hmow map mo mqommmm meHoHHHQ pm donopmm onMngo hp onH mmmm How mohoom pHQD smsmm one .mm mndem mHmEmm Ho Hopesz Om mmwmnmwmmmtmmmmmHmommUH anHmeH¢H mHmHHHQHo w m. w m 11 m m H _ HHmm F Hmassm _ . mQHHmm Ifl Hmqua _ HHmm # QOHpoSdopm mwm Ho Gomwmm 1.;«30 m 3.44:8 < 851 mm? .H 88508 lolo . mm Spam mm? .H 9388 II I. 18% mm? .H 5st pm... 2 8.18 mm? .H 9:6 I om .m 5 23% mm? .H is? m. 58m mm? .H 1,3159% n U 2:30< I mm ”1+ 8 153051 . on . mm . ow 155 Table 45. The Shell Thickness of Eggs Laid by Chickens Hatched at Different Seasons of the Year. (By Age of Birds). Hatching Season Period A B C D E F 24 15.5 25 12.8 26 15.6 27 15.7 28 15.1 29 15.1 15.5 50 15.2 15.5 51 15.6 15.6 52 15.8 15.5 15.1 55 12.9 15 5 15-5 54 15.8 15.6 15.4 55 15.5 15.9 15.6 56 15.8 15.6 15.2 57 15.0 15.7 15.2 14.0 58 15.0 15.7 15.6 15.2 59 15.5 15.8 15.0 15.5 40 15.7 15.4 15.8 15.6 41 15.5 15 O 15.4 15.6 15.7 42 15.0 15.4 15.8 15.5 15.0 45 15.0 15.7 15.5 15.5 12.7 44 15.5 15 2 14.0 15.9 12.9 45 15.1 15.4 15.8 15.4 15.5 46 15.4 15.5 14.0 15.5 15.5 15.5 47 15.7 15.6 15 5 15.1 15.5 15.5 48 15.7 15.8 15.1 15.9 12 4 12.9 49 15.1 15.2 15.7 15.5 15 5 15.4 50 15.6 12.7 15 8 15.1 15 4 l2 8 51 15.5 15.6 15.4 12.8 15.1 15 5 52 15.8 15.1 12.9 15.2 15 2 l2 9 55 15.5 15 5 15.2 15 0 12 5 54 15.5 15.7 15 0 15.5 12 2 55 12.7 12.8 15.0 15.6 15 5 56 15.5 12.8 12.5 15.2 12.8 57 15.4 15.4 12.7 15.4 15.0 58 15.5 15.4 15.5 15.2 12.4 59 15.6 12.9 15.4 15.4 60 15.0 12.5 15.7 12 8 61 14.0 15.1 12.8 15.2 62 15.2 15.1 12.9 65 15.5 15.2 12.8 64 15.1 15.4 15.5 65 12.6 15.0 12.8 66 14.0 12.2 .AmdnHm Ho owd hmv .HwoM on» H0 muomMmm onHmHHHQ #8 ocnopwm wanOHno an onH mmwm Ho mmonMOHga HHmnm was .um mmszm mUOHHmm qOHposconm em mm _ om mm mm Hm mm on we we 4: me 04 mm mm 4m mm cm 0 O O O O O O O b O 0 nopmm mmmH .H nonaoomn II.II. nopmm mmoa .H nonopoo II_II nopwm mmma H pmsmnd .I.I.I nopmm mmma .H mash I n I gopwm mm H «H HHHQ4 one... nopwm mmma H hgwsnpmm IIIIII nzmwmq qouI UB 10 sqqpuesnoqm u: sseuxorqm Itqu 155 Table 44. The Shell Thickness of Eggs Laid by Chickens Hatched at Different Seasons of the Year. (By Similar Date of Sample). Hatching Season . C D E F 1 15.0 15.8 15.1 15.5 2 15.0 12.9 15.2 12.8 5 15.5 15.8 15.6 15.6 4 15-7 15.5 15-5 15-7 5 15.0 15.8 15.5 15.1 6 15.4 15.7 15.6 15.5 7 15.7 15.7 15. 15.5 8 15.2 15.8 15.6 15.6 9 15.4 15.4 15.2 15.1 14.0 15.4 15.6 15.5 15.5 15.8 15.0 15.4 15.1 15.5 15.8 15.6 15.7 14.0 15.6 15.2 15.8 15.8 15.5 14.0 15.4 15.5 15.5 15.2 12.9 15.1 15.9 15.5 15.5 15.9 15.4 15.6 15.0 15.5 15.5 15.7 15.0 15.1 15.5 15.0 12.5 12.8 12.4 12.7 12.7 15.2 15.5 12.9 15.5 15.2 15.4 15.5 15.4 15.5 15.1 15.5 15.7 15.6 15.2 15.5 12.8 15.2 15.0 12.9 12.9 15.4 12.2 15.4 12.8 15.2 15.5 12.8 15.5 15.4 12.8 15.5 12.8 12.8 15.0 12.9 12.2 15.2 12.4 12.5 .Aonawm Ho opwn anHaHm hmv .Hon oAp Ho mnommmm pqmanHHn pm emnopwm maoMOHno Hp efimg mmmm Ho mmoQMOHna HHmnm may .mm onsmHm onamm Ho Hopasz om mmmmmmmm mm #mmmmmHmom mH wH 5H H H #HmH NHHH 0H m m m. m -U\ -¢ oxx -m -H fl HHdm _ Hoaasm — quHmm _ Hoana m. HmeII‘ qOHpoquHm wmm Ho nomwom .156 nopam wmmH .H umpamoon II.II. gopmm mmma .H nonopoo II II nopam mmmH .H pmsmsa .I.I.I nopwm mama .H muse I I I nopam mmmH .H HHHQH ...... nopwm wmmH .H mnwsnnom 81E qouI us JO sqqpussnoqm up sseuxorqm Iteqs 157 Table 45. The Percentage of Blood Spots Found in Candled Eggs Laid by Females Hatched at Different Seasons of the Year. Hatching Season Period A B C D E F H H w 0 HHHH H \N O1 H H H H l—‘ONI—‘l—‘OHNNI—‘HHHWHHNI—‘NHWPWNNNHWNNNHHI—‘N n O NHHONmeww#¢w#wwm#HHH HHHHHHH HHH mI—‘OHNHOl—‘I—‘ml—‘Hmm#ww-{rmNNNNNWN-PN oomoHHHHHHHHHHHmwwwmmeHmHHNNH HOD—'l—JOHNNl-‘WWW-P-PNNNWWWWW p m mmww¢mw¢w¢wmm Table 45. Continued. Period Hatching Season C p w D m HNOmeHmHH¢ HHHHHOHHHNH OOI—JI-Jm-lN—‘OOI-J OHHHHHH HOHH 1 The starting period of the extended lay observations as reported in the Experimental Design. 1 1.1.. 159 Table 46. The Blood Spots Found in Broken-out Eggsl Laid by Females Hatched at Different Seasons of the Year. (By Age of Birds). Hatching Season C D NNHHHWNOHHFWHPO¢OHOHHHWHNHOWNH w U1 0 OHONHNF‘HOOH‘P HWOOI—‘U‘lw owwmowwppwwwpwmomwmp#mmsww O‘F’Servations made of two dozen samples after candling en- lI‘e pen production. 160 Table 47. The Blood Spots Found in Broken-out Eggsl Laid by Females Hatched at Different Seasons of the Year. (By Date of Sample). Hatching Season D Sample A E F l 5 5 2 O 2 1 2 5 5 6 4 2 2 5 1 4 2 4 0 5 4 O 2 l 5 1 O 5 O 2 4 5 1 2 6 5 4 2 2 5 1 7 1 4 2 l 1 2 8 2 1 2 5 l 9 4 5 7 5 1 5 10 1 2 1 1 2 1 11 0 O 4 2 2 l 12 O 2 2 2 5 0 l5 1 l 5 5 5 l 14 1 l 1 l 4 0 l5 2 1 4 2 4' 4 16 l 1 1 1 1 0 l7 2 l O O 2 l 18 0 4 4 0 1 l 19 1 1 5 l 5 5 20 0 l .2 O 5 4 21 1 l 0 4 1 22 O 2 0 5 l 25 2 1 0 2 0 24 5 O 2 2 2 25 5 4 5 5 5 26 0 l 2 1 l 27 2 l 5 l 28 0 0 4 l 29 2 O 1 2 30 0 1 l 2 (Draservations made of two dozen samples after candling of eIitire pen production. 161 Table 48. The Monthly Cumulative Egg Production1 of Two Commercial Strains of Females Hatched at Dif- ferent Seasons of the Year. B St.II Season C Stu I of Hatch D St. I St.II F St. I St.II 20 28842 21570 21 29700 22141 22 50485 22810 25 51505 25456 24 52117 25886 15622 15740 16714 17702 18616 19597 19947 2 15247 17544 18566 27644 15902 17798 27458 28225 28970 16917 18856 20087 20885 21624 22441 25276 24626 15406 14065 ICalculated in dozens of eggs per 1000 birds housed. Table 49. The Monthly Cumulative Egg Size Distributionl 162 of Strain I Females Hatched on February 1, 1958. Mo. Cumulative Dozens of Eggs per 1000 Layers of Pee- Under Lay Jumbo X-Lg' Lg. Med. Sm. wee Grade 10 67 1498 4817 7926 2575 200 422 12 128. 2260 6105 8574 2575 200 621 15 165 2612 6659 8559 2575 200 720 14 204 2956 7156 8117 2578 200 798 15 255 5514 7581 8848 2578 200 895 16 289 5709 7952 8921 2578 200 971 17 559 4105 8269 8972 2578 200 1059 18 491 4486 8549 9005 2578 200 1158 19 650 5059 8867 9065 2578 200 1279 20 857 5497 9199 9145 2578 200 1588 21 915 5845 9470 9198 2578 200 1498 22 1017 6156 9756 9254 2578 200 1582 25 1120 6474 10012 9271 2578 200 1648 24 1205 6804 10281 9520 2578 200 1729 r— 1Calculated in dozens of eggs per 1000 birds housed. Calculated in dozens of eggs per 1000 birds housed. {Table 50. The Monthly Cumulative Egg Size Distribution1 of Strain I Females Hatched on April 1, 1958. hflo. Cumulative Dozens of Eggs per 1000 Layers <31? Pee- Under 1133’ Jumbo X—Lg. Lg. Med. Sm. wee Grade 10 104 985 5911 5971 2286 501 448 1L2; 124 1590 4765 6441 2511 501 614 l 3 142 1596 5140 6647 2520 501 704 14 172 1859 5494 6775 2529 501 785 -1-55 222 2115 5785 6874 « 2555 501 865 -3L€5» 262 2566 6056 6976 2556 501 924 l 7 556 2660 6550 7085 2556 501 1005 l 8 574 2867 6564 7145 25 58 501 1081 l 9 415 2986 6716 7128 2558 501 1120 駧<:> 445 5170 6915 7247 2558 501 1156 a l 477 5554 7157 7552 2541 501 1199 :22 515 5586 7407 7417 2541 501 1245 éggizs 547 5796 7656 7518 2541 501 1297 <4 585 5954 7801 7599 2541 501 1541 2E:~——— 165 Table 51. The Monthly Cumulative Egg Size Distribution1 of Strain II Females Hatched on April 1, 1958. Mo. Cumulative Dozens of Eggs per 1000 Layers of Pee- Under Lay Jumbo X-Lg. Lg. Med. Sm. wee Grade 10 259 2608 4478 4112 1192 168 825 12 525 5556 5508 4572 1202 168 1051 15 587 5715 5659 4479 1202 168 1104 14 496 4107 5991 4544 1202 168 1194 15 611 4461 6275 4612 1202 168 1289 16 697 4825 6505 4651 1202 168 1551 17 796 5057 6659 4668 1202 168 1597 1Calculated in dozens of eggs per 1000 birds housed. Table 52. The Monthly Cumulative Egg Size Distribution1 of Strain I Females Hatched on June 1, 1958. .Mo. Cumulative Dozens of Eggs per 1000 Layers of Pee- Under Iey' Jumbo X-Lg. Lg. Med. Sm. wee Grade 10 58 665 5968 7597 2229 261 489 1 2 75 1151 4958 8058 2250 261 651 1 5 112 1480 5479 8247 2255 261 752 14 148 1862 5914 8589 2264 261 816 l 5 192 2116 6217 8508 2264 261 888 l 6 250 2541 6556 8575 2264 261 967 l 7 274 2561 6882 8657 2264 261 1050 l 8 506 2784 7208 8746 2264 261 1065 l 9 545 5105 7646 8925 2270 261 1145 20 582 5597 8096 9126 2276 261 1255 2 l 402 5657 8409 9282 2284 261 1297 22 448 5905 8666 9564 2288 261 1575 2 3 478 4150 8928 9441 2288- 261 1428 24.. 522 4598 9175 9515 2288 261 1485 3L\ _ , <:Balculated in dozens of eggs per 1000 b1rds housed. L 164 '(Zalculated in dozens of eggs per 1000 birds housed. Table 55. The Monthly Cumulative Egg Size Distributionl of Strain I Females Hatched on August 1, 1958. Mo. Cumulative Dozens of Eggs per 1000 Layers of Pee- Under Lay Jumbo X-Lg. Lg. . Med. Sm. wee Grade 10 50 728 5575 7409 5080 555 707 12 77 1247 4457 7722 5086 555 874 15 111 1595 4927 7912 5086 555 1004 14 151 1870 5455 8004 5086 555 1158 15 180 2175 5865 8092 5086 555 1256 16 211 2506 6518 8204 5086 555 1558 17 250 2827 6819 8544 5086 555 1459 18 294 5257 7448 8554 5086 555. 1548 19 555 5598 7966 8764 ' 5086 555 1645 20 585 5898 8515 8840 5086 555 1759 21 448 4194 8656 8920 5090 555 1815 22 498 4515 8922 8974 5090 555 1869 25 569 4857 9172 9011 ' 5090 555 1956 1Calculated in dozens of eggs per 1000 birds housed.‘ {Fable 54. The Monthly Cumulative Egg Size Distributionl of Strain II Females Hatched on August 1, 1958. Ado. Cumulative Dozens of Eggs per 1000 Layers of Pee- Under llay’ Jumbo X-Lg. Lg. led. Sm. wee Grade JLC) 187 1789 5125 6640 1947 257 972 JLEB 508 2675 5750 6760 1947 257 1177 3L3; 447 5157 6105 6846 1947 257 1550 JL<+ 502 5494 6555 6882 1947 257 1446 l 5 569 5768 6618 6950 1947 257 1555 31-65 645 4119 6879 6971 1947 257 1625 31.2: 722 4491 7142 7017 1947 257 1700 l 8 876 5058 7570 7095 1947 257 1825 EIT“’ 165 Table 55. The Monthly Cumulative Egg Size Distribution1 of Strain I Females Hatched on October 1, 1958. Mo. Cumulative Dozens of Eggs per 1000 Layers of Pee- Under Lay Jumbo X—Lg. Lg. Med. Sm. wee Grade 10 121 1181 4555 7775 2217 215 667 12 192 1965 5298 8154 2217 215 871 15 255 2279 5774 8222 2217 215 986 14 267 2616 6188 8517 2217 215 1047 15 501 2905 6542 8420 2217 215 1116 16 555 5262 6954 8551 2221 215 1185 17 405 5616 7559 8680 2221 215 1274 18 446 5840 7561 8749 2221 215 1556 19 524 ‘4086 7766 .8785 2221 215 1592 20 575 4565 7949 8828 2221 215 1454 21 640 4642 8127 8851 2221 215 1481 1Calculated in dozens of eggs per 1000 birds housed. {Fable 56. The Monthly Cumulative Egg Size Distribution1 of Strain I Females Hatched on December 1, 1958. 1&0. Cumulative Dozens of Eggs per 1000 Layers of Pee- Under 1Lay Jumbo X-Lg. Lg. Med. Sm. wee Grade :Lc> 95 562 2782 6296 5612 1219 894 3L22 105 890 5866 6681 5617 1219 1071 1L2: 119 1074 4560 6869 5622 1219 1149 JL‘+ 155 1247 4796 7085 5651 1219 1212 -J_:5 (148 1464 5286 7509 5655 1219 1505 41~€5 175 1702 5666 7486 5655 1219 1405 l '7 215 1951 5955 7555 5642 1219 1465 31~Es 255 2204 6216 7598 5642 1219 1506 :1f a regular pattern of larger numbers of blood spots in 13he eggs laid by birds hatched during different seasons of 13he year. The larger numbers of eggs with blood spots 00— <311rred during a period corresponding to the late summer, fall and winter months of egg production regardless of ESeeason of hatch. No explanation can be offered why these IE>Toservation that, following these seasons, the incidence <>:f detectable blood spots in the eggs dropped to unimpor- ‘t3aant numbers again. An explanation might be forthcoming 178 if the data on all hatches were continued to completion. The available data suggest that a season of production (fall and winter) effect increased the blood spot incid- ence. The season of lay seemed to have a greater influ- ence on the incidence of blood spots in the eggs than did the influence of the age of the bird. Further study is needed in the field of the production of eggs with blood Spots during these various seasons of laying. Total cumulative egg production per season of hatch was calculated t0_indicate probable egg production if cer- tain environmental factors were present. The data, as pre- sented, were performance records for the particular gene- 'bic strains studied. The cumulative egg size distribution vvas obtained under a particular set of environmental con- dlitions. It is not expected that like-performance could IJe secured from the birds of different hatch dates under Clifferent sets of environmental conditions. It was not Lkznown if the highest hatch-date record encountered was ‘tflie maximum performance that could be achieved under ideal <3<3mmercial conditions. Likewise, it was concluded that the 3L<>west hatch-date record was not obtained under completely Eidlverse conditions. These observations agree with conclu- £3ions advanced by Platt (1960) in New Jersey. Even though the data might have shown significant $3€3asonal hatch differences in the egg production of one 5713ar, the data of another year did not concur. flhen the 179 egg production from similar hatching dates were compared, the significant hatching seasons of one strain were not confirmed by the production records of another strain. Inspection of the data, relative to the cumulative dozens of eggs produced, indicates that even though there Were no consistent seasonal differences in total egg pro- duction, there were considerable differences between strains when egg size distribution was considered. The nu- merical advantages of more dozens of larger eggs laid by Strains II and IV were not offset by an inferior egg qual- ity, as measured by total undergrade eggs. The practical observation of the disadvantage of holding over birds for a second year of lay has been sug- gested by the financial compensation paid to the Burns' Ibultry Farm, Inc., under the Memorandum of Understanding (Appendix Table 1). The older birds, held over for the extended lay periods after 24 months of age, were found ‘to be deficient in comparative egg production to the zyounger birds. The deficiency payments were based on U. S. (Erade A large eggs and calculated at five cents per dozen Jeess than the Federal-State Market News Service Report 1?Ibm Detroit. Therefore, the economic disadvantage of holding old :klens over for a second year of egg production has been sub- SStantiated by the necessity of these deficiency payments ‘Ebased on only 50% egg production. Michigan State University 180 Extension poultrymen, for years, have advised Michigan poultrymen that 60% egg production was an average break- even point of profit in the poultry operation. The egg production and egg size distribution data for females hatched at two different seasons of the year (April vs. August, 1958) were compared using the actual egg prices which prevailed in Michigan during the produc- tion periods of these females. It was theorized that if expected egg prices were applied to monthly egg size dis— tribution patterns for females hatched at different seasons of the year, a break-even point might be calculated. As shown in Table 65, the April-hatched females laid a.total of 17,529 dozen eggs over a period of fifteen The August-hatched females laid a total The total months of lay. <>f 19,598 dozen eggs over a comparable period. Jreceipts from the sale of large eggs from the April—hatched iTemales were $96.41 more than the receipts from the August- llaitched females, although 98 fewer dozens of eggs were pro- Cilzced by April-hatched birds. . The April-hatched females produced 6874 dozen medium €5€§gs and the total receipts were 31901.59. Although the liligust—hatched females produced 1218 more dozens of eggs <>££ this size the income was identical to the April-hatched females ($1901.60). The total receipts would suggest that it is impor— tant that the poultryman buy his chicks in order to take 181 advantage of the high price season for large and medium eggs. This would mean that the poultryman should be cog- nizant of the egg size dietribution patterns which result from hatching chicks at different seasons of the year. The above calculations are representative of actual data. However, the poultryman would need to utilize ex- pected egg prices in planning hatching dates. Table 65. Estimated Receipts from Eggs Periods 1 During Selected Season of Hatch April August 1958 1958 Numbers of Dozens of Eggs in 15 Months of Lay 17,529 19,598 ENmbers of dozens of large eggs 8,122 8,2209 .Average price of large eggs 8 0.55 3 0.51 IReceipts from large eggs $2644.62 $2548.21 Ifiumbers of dozens of medium eggs 6,874 8,092 Atverage price of medium eggs 3 0.28 8 0.25 IReceipts from medium eggs $1901.59 $1901.60 Fhimbers of dozens of small eggs 2,555 5,086 Atverage price of small eggs 9 0.25 8 0.25 Iieceipts from small eggs 3 525.21 3 718.52 Total Receipts 35071.42 $5168. 55 8 0.29 3 0.27 Jtverage price of all eggs lCalculated in dozens of eggs per 1000 birds housed. CONCLUSIONS The analyses of the data, under the particular en- vironmental conditions of this study, have indicated that satisfactory egg production may be expected from females hatched at any time of the year. These results have sug— gested that the improved systems of poultry breeding, de- veloped through Federal, State and private research, have improved the predictability of egg production. This pro- gress in poultry breeding to the date of this study would be expected when one has reviewed the past egg production records. As an example: Thirty years ago, the average hen in the United States laid 121 eggs per year, while today, the average hen is annually laying 206 eggs or an increase of 85 eggs. As a result, 15 percent fewer hens on farms in 1959 produced 60 percent more eggs than their ancestors produced in 1950. It appeared that there were no consistent differ— iances in the basic shape of the total egg production pat- 13ern due to hatching chicks at different times of the year. Iiowever, as also reported by other workers, the factor of Else at sexual maturity in this study did affect the shape C>f the total egg production curve. There were significant ESeasonal hatch effects, involving some strains and one set <>f records, on total egg production. In other test years, Einalyses of the egg production data of the same commercial — 182 - 185 strain of birds indicated no significance of similar dates of hatch. Other complete annual representative seasons of hatch were also analyzed but they were not found to be significant. Therefore, it can be concluded that no con- sistent seasonal hatch effects on total egg production could be expected on the.basis of season of hatch alone. Location effects within the poultry farm, involving different pens of similar date of hatch and strain, were not significant according to the data analyses of this study. Comparable results were concluded to be expected in total egg production, if reasonably similar environmen- tal conditions were encountered by different pens of birds within the farm. The pullet year of egg production, at least, was concluded to be not pertinent to total egg production from the modern chicken kept under Optimum environmental con- ditions. Consideration of keeping the yearling hens over .for the second year of lay involved other factors. Egg tveight distributions between the eggs produced by females liatched at different times of the year were important. IEgg size decreased in the summer months as reported in 13his investigation of the extended lay periods. There were eaISO'differenceS in egg weight distributions between strains . Expected economic returns could be affected by sea- ESon.of hatch, but varying wholesale egg prices would 184 result in inconclusive expected returns from year to year. Any practical economic factor of holding over old hens was nullified, when the calculations were made for the cash payments for a mutually agreed-upon deficient egg produc- tion. ‘Given an individual poultry farm operator's cost figures for producing eggs plus expected egg production, then egg production patterns under optimum environmental m conditions could be derived for the determination of maxi- mum profit. It has been pointed out, however, that sea- sonal hatch effects on total egg production were not sig- nificant in this study. Therefore, it is recommended or 6 suggested that the poultrymanwould be further ahead Oper- ating in accordance with his market demands and facilities rather than based on a set calendar pattern; because over a series of years, the hatching date may not be of particu- lar economic importance. Seasonal effects of hatch date on albumen quality of’the eggs laid in the extended laying periods involved :in this study were not evident. Consideration of the egg Cluality data of this study indicated that the method in VVhich the eggs were handled was more important than the sage of the birds. The decline in average egg quality in 13he extended lay periods was not important in this study, Tbecause the average egg quality of the samples was A or IDetter. There was a great variation in the quality of eggs produced as the birds became older. 185 Studies of the shell thickness data of the eggs pro- duced by the hens in the extended laying periods demonstra- ted that the method in which the eggs were measured was more important than the effect of the bird's age on the shell thickness. NO important decline in shell thickness should be expected in 24 months of lay if reasonable man- agement practices were employed by the poultry farm opera- tor. Seasonal hatch effects on the incidence of detect- able candled blood spots were significant, when the period of egg production was involved. The larger numbers of .3 blood spots were found in the very late summer, fall and winter months regardless of date of hatch. The poultry farm Operator should consider this economic loss as ex- cessive when confronted with the choice of keeping year- ling hens over for a second year of lay. The different hatching date effects on total egg ;production, in total numbers of eggs produced, were not ssuggested. The results of this study indicate that: given (1) a set of hatching dates, (2) a particular year with (zertain environmental conditions, and (5) a modern strain <>f chickens, then certain egg production results were ob- isained in this investigation. Therefore, it can be con- <=luded that, given the modern laying pullet, it is best ' :for the poultryman to schedule his chick-starting dates éaccording to his market demands for egg sizes rather than On set calendar pattern. BIBLIOGRAPHY Abplanalp, H. 1957. Genetic and Environmental Correla- tions Among Production Traits of Poultry. Poultry Sci. 56:226—228. Bennion, N. L. and D. C. Warren. 1955. Temperature and its Effect on Egg Size in the Domestic Fowl. Poultry Sci. 12:69-82. Blyth, J. S. S., 1952. The Correlation Between Egg Number and Egg Weight in the Fowl: An Investigation of Its Inconstancy. POultry Sci. 51:254-268. Brant, A. W., and H. L. Shrader. 1952. How to Measure Egg I. Q. (Interior Quality). Bureau of Animal Industry, A. B. A. Circular PA-202, U.S.D.A. Bray, D. F., S. C. King and V. L. Anderson. 1960. Sexual Maturity and the Measurement of Egg Production. Poultry Sci. 59:590-601. Clark, T. B. 1940. The Relation of Production and Egg Weight to Age in White Leghorn Fowls. Poultry Sci. 19 3 61-66 0 Cotterill, O. J., and A. R. Winter. 1954. Egg White Lysozyme. 1. Relative Lysozyme Activity in Fresh Eggs Having Low and High Interior Quality. Poultry Sci. 55:607-611. Cunningham, F. E., O. J. Cotterill and E. M. Funk. 1960. The Effect of Season and Age of Bird on Egg Size, Quality and Yield. Poultry Sci. 59:289-299. IDawson, L. E., L. R. Champion, J. A. Davidson, and H. C. Zindel. 1955. Improving Egg Quality Through R.O.P. Breeders - A Progress Report. Poultry Sci. 52:896. IDawson, L. E., and C. W. Hall. 1954. Relationship Between Rate of Cooling, Holding Container and Egg Albumen Quality. Poultry Sci. 55:624-628. I>uncan, D. B. 1955. Multiple range and F tests. Bio- metrica, 11(1):l-42. , :?roning, G. F., and E. M. “unk. 1958. Seasonal Variation in Quality of Eggs Laid by Caged Layers and Their Sisters on the Floor. Poultry Sci. 57:215-225. — 186 - 187 Fry, J. L., and G. N. Newell. 1957. Management and Hold Conditions as they Affect the Interior Quality of Eggs. Poultry Sci. 56:240-246. Funk, E. M., and H. L. Kempster. 1954. Egg Weight in the Domestic Fowl. Missouri Agr. Exp. Sta. Bull. #552. Goodale, H. D. 1918. Internal Factors Influencing Egg ' Production in the Rhode Island Red Breed of Domestic Fowl. Am. Nat. 52:65-521. Gowe, R. S. and W. T. Wakely. 1954. Environment and Poul- try Breeding Problems. 1. The Influence of Several Environments on the Egg Production and Viability of Different Genotypes. Poultry Sci. 55:6919705. Grotts, R. F. 1956. Seasonal Variations in Egg Quality. M. S. Thesis, University of Missouri, 66 p. Gutteridge, H. S. and J. B. O'Neil. 1942. The Relative Effect of Environment and Heredity Upon Body Measure- ments and Production Characteristics in Poultry. II. Period of Egg Production. Sci. Agr. 22:482-491. Hale, R. W. 1952. Experimental Error in Laying Experi- ments. J. Agric. Sci. 42:547-552. Hale, R. N. 1959. Absence of Pen Effects in Laying Exper- iments on a Semi-Intensive Plant. Poultry Sci. 58:759. Haugh, R. R. 1957. The Haugh Unit for Measuring Egg Quality. U. S. Egg Poultry Magazine, 45:552—575. Harris, J. A. and H. D. Goodale. 1922. The Correlation Between the Egg Production of the Various Periods of the Year in the Rhode Island Red Breed of Domestic Fowl. Genetics 7:446-465. IIill, J. F. and A. N. Nordskog. 1956. Efficiency of Per- formance Testing in Poultry. Poultry Sci. 55:256-265. Iiunter, J. A., A. Van Wagenen and G. 0. Hall. 1956. Sea- sonal Changes in Interior Egg Quality of Single Comb White Leghorn Hens. Poultry Sci. 15:115-118. Iiutchinson, J. C. D. 1955. Effect of Hot Climates on Egg Weight. Poultry Sci. 52:692-696. -..~1}_-. ...—11.. ...-... 4.... .... .4..- .... —4 l ‘. I g ? l I O l 1 1 1 1 1 D i 1 ...... .... <. Appendix 6 Date Laid: 199 EGG QUALITY RECORDS Date Broken: SCORE HEIGHT GRAMS j SCORE P-— s -C REMARKS T111315, Appendix Table 7. Individual Pen Identification of Dupli- rains of Birds Used in Location cated St Analysis 200 Code Letter Actual Corporation Pen Identification Number 12-1 7-2E 5 6-1W 10-2 6-2 10-1 8-5 8-4 6-4 9-2 Appendix Table 8. Monthly Outside Temperature Rangesl at Flint, Michigan, 1958. Mean Outside ngperatures Mean Mean Month Maximum Minimum Mean January 29.6 15.4 21.5 February 26.5 10.9 18.7 March 41.2 27.5 54.4 April 59.4 54.5 46.9 May 69.1 41.1 55.1 June 72.5 49.6 61.0 July 79.8 59.2 69.5 August 80.2 55.9 68.1 September 71.4 49,9 60.7 October 62.6 41.0 51.8 November 48.8 51.1 40.0 December 27.5 8.2 12.8 Average Temperature 45.5 1Source — United States Weather Bureau, East Lansing, Michigan. nIcHIcaN sm‘rE UNIV. LIaRnRIEs IIHI “Ml Ill |||1 “I “MI W I! 1|” IN I." 111111 WI 1” WI 31293107883112