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THE MSU Is An Affirmative Action/Equal Opportunity Institution ‘ cMMma-ot EFFECTS OF CAGE VERSUS FLOOR REARING AND DIFFERENT DIETARY PROTEIN LEVELS ON PERFORMANCE AND CARCASS QUALITY OF CORNISH GAME HENS AND BROILERS BY Pronoti Robinson A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Animal Science 1991 65’2”¢ZM’ ABSTRACT EFFECTS OF CAGE VERSUS FLOOR REARING AND DIFFERENT DIETARY PROTEIN LEVELS ON PERFORMANCE AND CARCASS QUALITY OF CORNISH GAME HENS AND BROILERS BY Pronoti Robinson Four dietary protein levels (20%, 22%, 24% and 26%) were fed to cornish game hens (CGHs) and broilers raised on litter floor and in cages for 4 and 6 weeks, respectively. They were started at one-day of age on the experiment. Combined data from CGHs and broilers showed significant effects of protein (P<.001) and rearing (P<.0001) on feed efficiency, but not on live weight or feed consumption. Ration with 20% protein yielded highest percentage of Grade A carcasses in CGHs (P<.005). Rearing chickens on floor produced better carcass quality compared to cage system (P<.05). No significant correlations were detected between breast blisters or percent abdominal fat with live weight. Highest eviscerated weights obtained were 66.63% and 72.51% of live weight for CGHs and broilers, respectively. Cervical dislocation method of slaughter yielded a higher percentage of Grade A carcasses than did conventional method, but statistical analysis eliminated the influence of slaughter methods on carcass appearance (P<.05). To my parents and beloved husband, without whom and without whose prayers I could never have come this far, I sincerely dedicate this work iii ACKNOWLEDGEMENTS I would like to express my very special thanks and gratitude to my academic advisor, Dr. Sam Varghese for his support, encouragement and guidance throughout this work. My sincere appreciation is extended to Drs. Donald Polin, Roy Emery and Denise Smith for their participation in the Guidance Committee, for their valuable suggestions and contributions to this study. I would like to thank Dr. Cal Flegal for his advice and assistance in formulating experimental ration for broilers“ My thanks are also especially directed to Dr. Larry Dawson for his help in grading the carcasses and in the analyses of scoring system used to evaluate these. Grateful acknowledgement is made to Dr. John Gill for his helpful advice on statistical analyses. My special thanks to Peter Saama for his assistance in using the SAS Package employed in this research. I I take this opportunity to extend my special thanks to Coturnix International Inc. for providing funds to conduct this research study. iv LIST OF Chapter 1. TABLE OF CONTENTS ........................................... vii INTRODUCTION ...................................... 1 1.1 Need for the Study ..................... 2 1.2 Goals and Objectives of the Study ...... 3 1.3 Organization of the Study .............. 6 REVIEW OF LITERATURE .............................. 7 2.1 Introduction ........................... 7 2.2 Protein Requirements of Broiler Chicks ..................................... 7 2.3 Cage vs.Floor Rearing of Broilers ...... 12 2 4 Abdominal Pat in Poultry ............... 13 2.5 Breast Blistering in Broilers .......... 17 2.6 Processing of Broilers ................. 19 2.7 Meat Yield of Poultry .................. 24 OLOGY ....................................... 27 3.1 Experimental Design .................... 27 3.2 Experimental Diets ..................... 27 3.3 Methods of Experiment .................. 31 3.4 Analysis of Data ....................... 34 RESULTS AND DISCUSSION ............................ 37 4.1 Influence of Different Protein Levels on the Performance of Floor- and Cage- Reared Cornish Game Hens and Broilers ...... 37 4.1.1 Cornish Game Hens ......... 37 4.1.2 Broilers .................. 39 4.2 Effects of Dietary Protein Levels and Cage vs.Floor Rearing on Carcass Grading... 43 ' 4.2.1 Cornish Game Hens ......... 43 4.2.2 Broilers .................. 43 4.3 Breast Blistering in Cornish Game Hens and Broilers .......................... 48 4.3.1 Cornish Game Hens ......... 48 4.3.2 Broilers .................. 49 4.4 Correlation between Live Weight and Abdominal Fat (Expressed as a Percentage of Live Weight) in Cornish Game Hens and Broilers ................................... 51 4.4.1 Cornish Game Hens ........ 51 4.4.2 Broilers ................. 54 4.5 Correlation between Live Weight and Eviscerated Weight (Expressed as a Percentage of Live Weight) in Cornish Game Hens and Broilers .................... 57 4.5.1 Cornish Game Hens ......... 57 4.5.2 Broilers .................. 59 4.6 Effects of Slaughtering Methods by Cervical Dislocation or Conventional Method on the Appearance Grade in Cornish Game Hens and Broilers ..................... 62 4.6.1 Cornish Game Hens ......... 62 4.6.2 Broilers .................. 63 5. SUMMARY AND CONCLUSIONS ........................... 67 APPENDIX ............................................. 71 BIBLIOGRAPHY ......................................... 78 vi LIST OF TABLES Table Page 1. Experimental design for cornish game hens and broiler chick ......................................................... 28 2. Formula and chemical composition of,experimenta1 rearing rations during 0-3 week period ........................ 29 3. Formula and chemical composition of experimental rearing rations during 3-6 week period ........................ 3O 4. Scoring system for grading carcasses in cornish game hens and broilers ............................................. 33 5. Scoring system for evaluating blisters in cornish game hens and broilers ........................................ 34 6. Effects of protein levels on the performance of cage and floor reared cornish game hens ............................ 38 7. Effects of protein levels on the performance of cage and floor reared broilers ..................................... 4O 8. Analyses of variance of average body weight, feed consumption and feed efficiency ............................... 42 9. Percentages of carcasses in each grade, by Rearing methods (combined data) ....................................... 45 10. Percentages of carcasses in each grade, by Protein levels (combined data) ........................................ 46 11. Analyses of variance of carcass grading in cornish game hens and broilers ........................................ 47 12. Breast blister incidents in cornish game hens, by Rearing system ................................................ 48 13. Correlation coefficients between live weight and breast blisters in cornish game hens .......................... 49 14. Breast blister incidents in broilers, by Age and Rearing ....................................................... 50 15. Correlation coefficients between live weight and breast'blisters in broilers, by Age and Rearing ............... 51 16. Means and standard deviations of abdominal fat in cornish game hens ............................................. 53 17. Correlation between live weight and abdominal fat (expressed as a percentage of live weight) in cornish game hens ..................................................... 54 18. Means and standard deviations of abdominal fat in broilers ...................................................... 55 19. Correlation between live weight and abdominal fat (expressed as a percentage of live weight) in broilers ........ 57 20. Means and standard deviations of eviscerated weight in cornish game hens .......................................... 58 vfi 21. Correlation between live weight and eviscerated weight (expressed as a percentage of live weight) in cornish game hens ............................................. 59 22. Means and standard deviations of eviscerated weight in broilers ................................................... 6O 23. Correlation between live weight and eviscerated weight (expressed as a percentage of live weight) in broilers' ...................................................... 61 24. Percentages of cornish game hen carcasses in each grade (based on appearance) for each slaughter method ......... 62 25. Percentages of five-week old broiler carcasses in each grade for each slaughter method (based on appearance) ................................................... 63 26. Percentages of six-week old broiler carcasses in each grade for each slaughter method (based on appearance) ................................................... 64 27. Effects of slaughter methods on appearance grade in cornish game hens and broilers (combined data) ................ 64 31. Chi-square test of carcass appearance grade ............... 66 I. Means and standard deviations of live body weight in cornish game hens (0-4 weeks) ................................. 71 II. Means and standard deviations of live body weight in broilers ...................................................... 71 III. Means and standard deviations of cumulative feed consumption in cornish game hens (0-4 weeks) .................. 72 IV. Means and standard deviations of cumulative feed consumption in broilers ....................................... 72 V. Means and standard deviations of cumulative feed conversion in cornish game hens (O- -4 weeks) ................... 73 VI. Means and standard deviations of cumulative feed conversion in broilers ........................................ 73 VII. Means of eviscerated (RTC) and abdominal fat (AFT) weights in four-week old cornish game hens .................... 74 VIII. Means of eviscerated (RTC) and abdominal fat (AFT) weights in broilers ........................................... 74 IX. Percentages of cornish game hen carcasses in each grade, by Protein level and Rearing .......................... 75 X. Percentages of broiler carcasses (five-week old) in each grade, by Protein levels and Rearing ..................... 76 IX. Percentages of broiler carcasses (six-week old) in each grade, by Protein levels and Rearing ..................... 77 viii CHAPTER 1 INTRODUCTION The country where the author comes from and where she plans to return to serve her people, is Bangladesh. It is socio-economically one of the most underprivileged nations of the world. There are 110 million people crowded in a land, the size of which is about that of state of Wisconsin. Within a period of only a few years war, flood, famine, and deadly diseases, each in turn plunged a once pleasant and prosperous dbuntry to a land of poverty and starvation. With the beginning of a new day, thousands of new lives are born in this land without having any hope and little food, education, health care, a roof overhead, or even a job assurance for the future. Nutrition, for many, is inadequate to improve the quality of life, and in most cases, is barely adequate to support life. In spite of many limitations, the Government of Bangladesh and other non-governmental organizations are making efforts to improve the nation's economic conditions. There are areas where potential developments can be made-- poultry production is such an area. 1.1 Need for the Study Bangladesh has a very old history of domestic poultry rearing. Almost every village in Bangladesh has poultry that contribute a nominal portion of the income for rural households. According to an estimate by Okada et al. (1988), there are about 60 to 70 million chickens in Bangladesh. Between 1960 and 1970, the poultry population had fluctuated about 19 million to 20 million. The cyclonic storm in 1970 and the war of independence in 1971 destroyed a substantial number of livestock including more than 1 million chickens (Nyrop et a1., 1975). The chickens in Bangladesh consist mostly of a nondescript indigenous type called 'Deshi' chickens (Okada et a1., 1988). These birds are medium in size (1.0 to 1.4 kg.), produce few and small sized eggs, and are raised for both eggs and meat. All of the operations related to their raising are conducted on a small scale with traditional village practices. They are generally raised by the 'free method' (Obaidullah, 1969). They roam freely like scavengers and collect food from backyards, gardens, and fields. The chickens sustain themselves on household scraps, grain left over in the fields and gardens, vegetables, insects, etc. Occasionally they are given small quantities of broken rice or rice husks. Although there is a tremendous need to improve poultry production in Bangladesh, no attention or research was accomplished in this discipline. No significant work is 3 being done to utilize chickens for providing food or for economic improvements among the poor rural farmers and their families. The main hindrance is that Bangladesh like other less developed countries has a small number of technically trained people and a shortage of support services to accomplish such an undertaking. Today Bangladesh needs well trained personnel with expertise to promote modern scientific ideas and technology in order to improve the production of farm animals. There is a great need for adequately trained people to organize, modernize, and manage poultry farms in Bangladesh. Lack of technical knowledge in this vital aspect of national development has resulted in a significant loss of economic growth. This author desires to take back home with her adequate and effective training, to improve the nutrition of her people. Bourne (1980) justifies this need in the following words: "It is desirable that the thesis research problem of the graduate student be on a topic that is appropriate for their work when they return to their home country. Many students return to their countries with an advanced degree unable to relate to the research needs and possibilities in their own country. If their thesis research relates somehow to the needs of their country, they have at least a start on the right track" (p. 52). 1.2 Goals and Objectives of the Study In the past, in developing poultry rations, main enuphasis was given to formulate feeds which would produce a maximum biological efficiency, that is, highest live weight gadJn and best feed conversion. However, the concept that 4 'better the feed conversion, the more efficient the producer' is not always true. The main goal for a poultry meat producer is to achieve maximum profit. The highest live weight gain and better feed efficiency does not always give the highest profit (Wegner, 1977). This is because, the main factors that determine production costs of poultry are growth rate and feed costs per unit of growth (Leenstra, 1989). Since feed cost represents 70% of the total cost of production (Charles, 1980) and protein is one of the most expensive item in the cost of a complete feed, every effort should be made to reduce its use without lowering the performance of chickens at the same time. For a country like Bangladesh with minimal cereal grain resources and low availability of protein, it was deemed necessary to identify minimum protein level that would satisfy the nutritional requirements of the chickens, and at the same time produce optimum performance. Also, from the standpoint that many farmers in Bangladesh do not have enough land to establish and maintain even small backyard poultry operations, the practicality of using cages as an effective housing method for raising poultry to a certain age needed to be evaluated. Again it is becoming increasingly important to consider not only weight gain, feed conversion, feed costs or combinations of these factors, but also the carcass quality of meat animals. In recent years there has been an increased concern over excessive fat deposition in chickens. Abdominal fat adds little to overall carcass quality and in some cases l 5 are considered as waste. High amounts of abdominal fat can reduce processing yields since it is often removed from the carcass together with the intestines during processing. The relationship between eviscerated carcass weight and live body weight is an important measure of efficiency in poultry processing (Jaap et al., 1950), and it appears that much more research is needed to identify the various factors affecting meat yield of poultry. Again, in a country like Bangladesh where most villages have no electricity, the feasibility of applying electrical stunning prior to conventional slaughter may be impractical. In that case the feasibility of incorporating a new slaughter method such as cervical dislocation, and its effect on bleeding and carcass appearance needed evaluation. Considering these goals, the primary objectives of this research were designed to study 1) the effects of different dietary protein levels and rearing methods (eg., cage and floor housing) on the ' performances of cornish game hens‘ and broilers. Factors to be evaluated are a) body weight, b) feed consumption, c) feed efficiency, d) breast blisters and e) carcass grading; 2) the influence of slaughter method (conventional vs cervical dislocation) on carcass appearance; ‘A cornish game hen is a young immature chicken weighing not more than 2 lb (0.9 kg) dressed, which means the live market weight should be between 2.25 and 2.50 lb (1.02 and 1.14 kg). Normally, it takes from 4 weeks and 4 days to 5 weeks of growing time for bird to \reach the desired weight and is prepared from a Cornish chicken or the progeny of a Cornish chicken crossed with another breed of chicken. ' 6 3) the correlations between live weight and incidence of breast blisters, percent abdominal fat and eviscerated weights. 1.3 Organization of the Study Including the introductory section, this thesis is divided into five chapters. Chapter 2 is concerned with the review of literature pertinent to the present study. The experimental design, diets, general description of the experimental methods, and means for statistically analyzing the data are outlined in Chapter 3. Chapter 4 discusses the principal findings regarding the effects of different dietary protein levels on cornish game hens and broilers, comparison between cage and floor housing systems, and also the influence of slaughtering methods on carcass appearance. The last chapter summarizes the findings and provides the conclusions. CHAPTER 2 REVIEW OF LITERATURE 2.1 Introduction The review of literature pertinent to the topic under investigation is divided into six sections. The first section is the protein requirements of broiler chicks. The second section covers the cage vs. floor rearing of broilers. The third tOpic is the abdominal fat in poultry. The fourth section deals with the breast blistering in broilers. The fifth area is the processing of broilers, and the last section focuses on the meat yield of poultry. 2.2 Protein Requirements of Broiler Chicks Poultry derive their protein requirements from cereals as well as from the protein-rich foods (Feltwell and Fox, 1978). The dietary protein requirement is actually the requirement for amino acids contained in the protein. Although some amino acids can be produced within the body of the bird by the transformation of other amino acids, some of the amino acids are essential in the sense that these have to be provided by the dietary protein or as dietary supplements since the bird cannot synthesize these. Therefore, the protein requirements have two parts, (i) the essential amino 7 8 acids needed by the bird because it cannot synthesize these, and (ii) sufficient protein to supply either the nonessential amino acids themselves or to supply amino nitrogen for their -synthesis. Various workers have studied the quantitative relationship between available calories in poultry rations and their protein content. Subhaschandran and Balloun (1969) reported that the protein requirements of poultry increase as the energy content of the diet increases, and these requirements, therefore, can no longer be expressed as percentage of diet but rather should be expressed as energy to protein ratio. The concept of the energyzprotein ratio was developed as a simple means to balance the protein and energy contents of broiler and hen diets (Combs and Romoser, 1955). The latter workers observed that chicks fed on high energy diets needed higher dietary protein contents than those fed on low energy diets for maximum growth. Hill and Dansky (1950) found that growth was reduced when a high energy and low protein ration was fed, but that growth was restored when the energy level was lbwered. Sunde (1956) showed that a ration high in protein and low in energy caused a reduction in the growth rate and a reduced efficiency of feed utilization. Raising the energy level of this ration by the addition of fat improved both growth and feed efficiency. It can therefore be concluded from these studies that when the percent protein in the diet is high, 9 the energy level must be high. When the protein level is lower, the energy level can be lower. Donaldson et al. (1956) demonstrated improvements in growth and food utilization of chicks as a result of increasing dietary protein content. Nakamura et al. (1988) used three energy levels, 2900, 3100 and 3300 kcal. metabolizable energy (ME)/kg., and three protein levels of 16%, 19% and 22% to formulate nine grower-finisher rations fed to broilers. They found that when protein level was high, weight gain and feed efficiency progressed. Gowda (1973) examined the performance of broiler chicks at four levels of protein (15%, 18%, 21% and 24%) from 1—7 weeks. All diets were isocaloric having 3000 kcal. ME/kg. In their study, 24% dietary protein gave maximum weight gain. Efficiency of feed utilization was also improved by increasing protein level of diet. Similar observations, that, broiler growth increases with increasing dietary protein content were also made by Matterson et al. (1955), Leong et al. (1959) and Pesti and Fletcher (1983). By reviewing these literature one can conclude that growth and feed efficiency of broilers improve with increasing dietary protein content. These findings, however, are contradictory with the result reported by Summers and Leeson (1985). Feeding a range of dietary crude protein levels (16% to 22%) during the 28 to 49-day period, these workers found that crude protein level had little influence on male broiler body weight gain and feed conversion. The chicks offered 18% crude 10 protein diet gained significantly more weight during this period than those receiving a 22% crude protein diet. Subhaschandran and Balloun (1969) reported that protein requirements of chickens are highest after hatching and begin decreasing after 6 to 8 weeks. Twining et al. (1974) reported that broiler chicks receiving a low protein starter had a lower body weight and feed conversion at 4 weeks of age as compared to those receiving the required level. Levels of dietary protein used in rations fed to growing broilers are extremely variable. Singh (1972) recorded better growth and feed efficiency in broiler chickens with a protein level of 24% having a C/P ratio of 125:1. Sunde and Bird (1959) found that the protein requirement of chickens fed a ration containing 1760 kcal. productive energy/kg. was 20% to 21% from 0 to 6 weeks of age. Singh et al. (1978) reported that highest body weight of broiler chicks was obtained with mash containing 24.6% crude protein and 2745 kcal. of metabolizable energy, whereas the lowest body weight was obtained with mash having 29.1% percent protein and 3166 kcal. metabolizable energy. These results are in close agreement with the findings of Lewis and Morgan (1963) who found the protein and energy levels of 24.9% and 2700 to 2900 kcal ME/kg. to be optimum for growth of broiler chicks. Prasad et al. (1973) conducted a 2x4 factorial experiment with one-week old commercial crossbred broiler chicks using diets containing two protein levels (19.9% and 23.2%) and four calorie (ME): protein rations (143, 153, 134 11 and 122). As both protein and energy levels were increased, corresponding improvements in weight gain and feed efficiency were observed. The favorable responses in weight gain and feed efficiency were significant (P<0.05) when metabolizable energy (ME) was increased from 2834 to 3044 kcal/kg. at 19.9% protein but not at 23.2% protein. Panda and Reddy (1976) reported that starting broiler chicks require about 23%-24% protein with an energy content of about 3100 kcal. ME/kg. diet. From the results of these studies one can conclude that protein requirements of broiler chicks during the starting phase for optimum performance is above 20%, and probably around 24% with an energy concentration of 2700 to 3100 kcal. ME/kg. diet. Nagabhushanam et al. (1979) tested four protein levels (18%, 20%, 22% and 24%), each having four dietary energy levels (2520, 2430, 2340 and 2250 kcal. ME/kg.) in commercial starter chicks. Based on their findings, the authors reported that during summer, caloriezprotein ratios ranging from 2250:24 to 2520:24 gave maximum weight gains and feed efficiency while during winter, calorie: protein ratios ranging from 2250:22 to 2430:22 gave adequate body weight gains and feed efficiency. The protein utilization was maximum on 18% and 22% levels during summer and winter respectively. Cilly et al. (1973) studied the effect of season (summer and winter) on protein and energy requirements of White Leghorn chicks. Four protein levels 17%, 19%, 22% 12 and 25% were fed each at three levels of energy, i.e. 2400, 2700 and 3000 kcal. ME/kg. It is apparent from their data that the performance of the chicks was better with 22% protein at an energy concentration of 2400 and 2700 kcal. ME/kg. in summer: The same energy concentration was satisfactory in winter also but at a higher level of protein, i.e. 25%. These data indicate that the protein and energy requirements of broiler chicks are different during summer and winter months. 2.3 Cage vs. Floor Rearing of Broilers. A large amount of investigational work has been done on broilers in cages. Body weight, mortality, breast blisters, carcass quality and feed conversion comparisons have been made with birds grown on litter. Andrews et al. (1975) found no significant difference (P<0.05) between cage- and floor- reared broilers. Their 8-week body weights were 1513 and 1485 grams per broiler, respectively. Breast blisters were found on only 1.5% of the caged broilers. The floor—reared broilers were checked for breast blisters, enlarged feather follicles and leg problems; but the incidences were negligible. Significant differences in body weight were noted between birds of different tiers in cages. The broilers, at 8 weeks of age in tiers 2 and 3 were heavier (P<0.01) than those in the bottom or top tiers. These authors concluded that with the technology available at that 13 time, small broilers could be grown successfully in cages as Rock Cornish Game Hens with certain limitations. With proper cage floor breast blisters could be eliminated. Welch et al. (1970) found that body weights of both males and females grown to 56 days of age in cages were lower than the body weights of birds reared on floor with litter. Breast blisters were present in 83% of cage-grown birds examined. . Andrews and Goodwin (1973) observed no statistically significant differences for 8-week live body weights among the floor- and cage-reared broilers. At 9 weeks of age, birds on the second and third tier of cages were significantly heavier (P<0.05) in live weight than the birds in the other tiers, or on the floor. No significant difference was found among the cage- and floor-reared broilers for feed efficiency. It is therefore apparent from the reports of these workers that when feed efficiency and broiler live weight are considered, there is no significant difference between cage and floor housing methods. Breast blisters are said to exist only in cage-grown birds, which however can be eliminated with proper flooring material. 2.4 Abdominal Fat in Poultry Fat is considered as an important factor which influences the quality of a poultry carcass. In recent years there has been an increased concern over excessive fat 14 deposition in broilers. The main fat depots are located beneath the skin, in the abdominal cavity, and especially around the viscera. Although skin fat, including the depot areas on the breast and back, are essential for acceptable human consumption qualities, visceral and abdominal fat add little to overall carcass quality and are considered as waste product. Kubena et al. (1974) pointed out that "Deposits of fat in the abdominal area of the broiler are considered a waste product in the poultry industry since some of the fat is freed from the carcass during processing. Not only is the abdominal fat a loss, but it represents an added expense since pollution control requires that the added fat be removed from processing plant water. Some of the fat adheres to portions of the digestive system and is reprocessed as a component of poultry-by-product meal. The loss in this case is the difference in the cost of production of this fat and its value as a component of the poultry-by-product meal. Some of the fat adheres to the carcass of the processed broiler. In further processing such as frying, it would appear that the larger the quantity of fat, the greater the cooking loss" (p. 211). Fat deposition can be influenced by environmental factors and to a larger extent by nutritional and genetic factors. Among environmental factors influencing fat deposition are housing systems: broilers grown in cages have a higher fat content than broilers reared on litter (Deaton et al., 1974); and temperature: moderately high temperatures give fatter broilers compared to low temperatures (Kubena et al., 1974). Goodwin (1980) reported that the amount of abdominal fat which comprises from 2% to 4% of total body weight in today's broilers is influenced by several factors such as genetics, nutrition and sex. Differences among 15 commercial broiler strains in abdominal and carcass fat provide partial evidence that these morphological traits are influenced by heredity. Middelkoop et al. (1977) tested two commercial parent lines and six commercial crosses. They found considerable differences in abdominal fat, between the two sexes and among the stocks from different breeders, but not between strains from the same breeder. I A review of the literature by Kubena et al. (1974) reported that the dietary energy level of the starter diet influences the quantity of abdominal fat in both sexes i.e., as dietary energy level increases, the quantity of abdominal fat in broilers increases. Also, within each dietary treatment, the abdominal fat in females was of a higher percentage of body weight than in the males. Essary et al. (1960) reported that when birds acquire energy in excess of their normal metabolic needs, fat deposition occurs. A considerable portion of this fat is deposited in the abdominal area. Experiments conducted by Deaton et al. (1981) showed that as the dietary fat level increased, the amount of abdominal fat in broilers increased under both a moderate and a high temperature rearing regimen. Griffiths et al. (1977), however, did not observe an increase in abdominal fat as dietary fat level increased. Thus, this relationship between the dietary fat level and abdominal fat deposition in broilers remains inconclusive. 16 Summers and Leeson (1979) indicated that energy intake, rather than dietary energy level, is the main factor which influences abdominal fat deposition. Diets of equal energy content but different in amount of protein resulted in marked differences in abdominal fat, pointing out that carcass fat content can be reduced by dietary means; however, the cost of higher dietary protein levels can be uneconomical. The estimation of fat in chickens usually involves laborious and time consuming procedures. Becker et al. (1979) reviewed several methods of fat estimation that have been designed to lower cost and time involved in estimation of fat in broiler chickens and identified abdominal fat weight as an excellent predictor of total, carcass, and intestinal fat. These authors justified their results in the following words "The correlation coefficients and the squares of the coefficient, r2 (which gives the proportion of the variance of a trait attributable to the relationship with another trait) between the two traits and the various measures of fat in the chicken shows that the abdominal fat or percent abdominal fat had a higher correlation in every comparison, both male and female. Even when abdominal fat weight was eliminated from total fat to avoid a part-whole relationship the comparison favored the use of abdominal fat vs. percent backskin fat. It took 8 min. to dissect, weigh, and record abdominal fat; the backskin procedure required about 7 to 8 days....On the basis of statistical considerations, time and cost abdominal fat was superior to measuring backskin fat for predicting total, carcass, and intestinal fat" (p. 840). Sonaiya (1985) reported abdominal fat weight as the .\~‘ best predictor of total body fat weight. Whenever difficulty 17 of operation and time are constraints to fat estimation, the measurement of abdominal fat thickness is highly recommended in predicting total body fat content. From the findings of these experiments it can be concluded that abdominal fat constitutes about 2% to 4% of total body weight and is the best predictor of total body fat weight. It is influenced by a number of factors such as housing, temperature, heredity, nutrition, sex, dietary energy level and energy intake. 2.5 Breast Blistering in Broilers Considerable research has been done to overcome the occurrence of breast blisters in broilers. Breast blisters are said to be influenced by a number of factors: (1) an abrasive action of litter on the breast while the bird is resting, (2) an irritation of the breast by manure and litter, (3) a combination of (l) and (2). Heavy broilers are usually older and are exposed to the abrasive action or irritation of the litter for a longer period of time and therefore there is a tendency for heavier birds to have more breast blisters and bruises (Smith, 1956). Breast blisters are said not to exist in birds reared on metal floors normally used for pullet rearing (Brown, 1969). His data suggested an average target weight of 1.64 kg. per bird as being the most suitable for cage rearing, without giving rise to breast blister formation. Lloyd (1969) showed that broilers weighing 1.70 kg. and 1.81 kg. 18 reared on wire resulted in downgrading of 21.7% and 27.3% respectively due to breast blisters. Proudfoot et al. (1979) reported that the percentage of birds graded down because of breast blisters increased linearly as stocking density increased. This trend was significant at the 5% level of probability for females, and approached significance at the 5% level for males. Experiments conducted by Welch et al. (1970) confirmed that breast blistering is significantly correlated with bodyweight and that blister score can be predicted for cages with metal floors. They found the incidence of breast blisters to be 68% to 91%, 55% to 82%, 60% to 67% and 2% to 10% on broilers reared on wire floors, wood slats, plastic mesh and litter, respectively. Andrews (1972) performed experiments with broilers to ascertain the feasibility of growing broilers in cages. He found that broilers reared in cages with rubber covered nylon floors (RCN) had no blisters when compared with plastic mesh. Andrews and Goodwin (1973) observed similar results of practically no blisters in 8-week old birds grown in cages on RCN floor compared with birds reared on plastic mesh. It can be summarized from the results of all these experiments that broilers could be grown to heavy weights in cages, under crowded conditions without an incidence of breast blisters and without any detrimental effect to body weight when RCN is used as a flooring material. 19 2.6 Processing of Broilers Broiler processing is a system of complex steps to convert the live bird into a ready-to-cook product either as a whole bird or cut up into component parts. Preparing poultry in a ready-to-cook form involves live bird catching, cooping and hauling, holding live birds on a truck, unloading, hanging on the conveyor, stunning, slaughtering, defeathering, eviscerating, inspecting, chilling, grading, packing and finally shipping. The marketing of ready-to-cook poultry became significant during the 1930's, and rapid expansion began during the 1940's. Today, ready-to-cook poultry is available throughout the country because of the advancements in the highly commercialized operation of killing, dressing, eviscerating, grading, packaging and rapid transportation of the meat to distant markets (Taylor and Helbacka, 1968a). A major concern during assembly of poultry is the minimizing of bruises on the carcass. Field studies revealed that considerable bruising occurs in the poultry house before the catching crews arrive (Cox, 1981). Hewell (1986) reported that up to 50% of downgrading bruises can occur in the broiler house prior to catching Operations. Hamdy et al. (1961) reported that 90% of all bruises were less than 12 hours old. Goodwin (1986) stated that most bruises occur within 12 to 24 hours prior to processing. Some of the reasons listed by Goodwin (1986) are house construction, equipment placing and management factors such as not allowing 20 feeders to run empty during the final 24 hours, or failing to have the house ready when the catching crews arrive. Childs et al. (1969) reported that 58.4% of bruises on the breast and legs, of severity sufficient to require downgrading because of trimming, occurred prior to catching operations. Taylor and Helbacka (1968b) found significant differences among catching crews as to the numbers of bruised birds. In their studies of over 6000 flocks, percentages of bruised birds varied by monthly averages from 16.6% to 28.4% over a two year time span. These authors also reported about 1% fewer bruises on birds loaded in the dark as compared to daylight loading. It is therefore apparent from these reports that bruising is usually attributable to house construction, equipment placing, rough handling of birds during catching, cooping, loading, unloading, time of the day and number of catching crews. Brant et al. (1982) reported that withdrawal time for feed and water is about 10 hours. Live bird shrinkage can range from 0.3% to 0.5% per hour for the first 12 hours off feed and will average approximately 0.2% per hour over a 24- hour period. Furthermore, the incidence of fecal contamination can be kept to a minimum when the total feed and water withdrawal time is from 8 to 12 hours. Wabeck (1972) reported a linear relationship between percentage shrinkage and the time off feed. Sathe and Khan (1970) observed that the birds held in crates without food and water 21 lost 10% of live weight in 20 hours and the dressing yield from those birds was significantly lower after 12 hours fasting. Sahoo et al. (1974) reported that broilers held in a cool and well ventilated place without food, bedding and litters, even though plenty of drinking water was allowed, lost 4.91% to 6.66% of live weight at 16 to 18 hours fasting. The dressing yield in these fasting birds was 0.94% to 2.82% lower than the birds which were slaughtered without fasting. From these studies it can be concluded that prior to killing, birds should be allowed sufficient time to clear the digestive tract without extending the time to the point that would reduce the yield of salable product. Stunning is required for all animals prior to slaughter by U.S. law. The method of choice in the poultry industry is electric shock. Stunning is essential for satisfactory bleeding and feather release (Brant et al.,l982). The total and relative amount of blood loss through bleeding has always been of interest with respect to the appearance of the dressed poultry as well as from the economic standpoint (Newell and Shaffner, 1950). Blood loss must be maximum at the time of slaughter, and is a desirable characteristic of any animal slaughtered for human consumption. Kotula and Helbacka (1966b) reported that salable parts of chickens contained 36.7% to 45% of the total blood of the live bird. Carcass appearance grade may be lowered when veins containing excessive amounts of blood are ruptured, thus giving the 22 appearance of a bruised carcass. This author has not found any improvement on these figures in recent years. Newell and Shaffner (1950) endeavored to increase the blood loss of New Hampshire chickens by subjecting these to three slaughter methods: (1) Kosher slaughter, (2) debraining by inserting a knife through the mouth, and (3) beheading. Kosher slaughtered birds lost the greatest amount of blood, followed by those that were debrained, and then by those that were beheaded. Davis and Cole (1954) used five slaughter methods in a bleed out study with Leghorn broilers: (1) single carotid artery and jugular vein cutting, (2) both carotid arteries and jugular vein cutting without severing the wind pipe, (3) beheading, (4) debraining with both carotid arteries and jugular vein cutting, and (5) stunning .by striking the head with a stick and then both carotid and jugular vein cutting. Kotula and Helbacka (1966a) made an effort to study the variation in blood loss over the different time intervals in commercial broilers. The slaughter methods used to kill these birds were: (1) electrical stunning and standard cutting, (2) debraining followed by standard cutting, (3) captive bolt stunning followed by a standard cutting, (4) carbon dioxide immobilization followed by a standard cutting, (5) severing of both jugular veins and carotid arteries, and (6) slaughter by a standard cutting. These workers found that the greatest bleed out came from birds which had been mechanically stunned before slaughter, whereas in Davis and Cole's (1954) 23 experiment mechanically stunned birds gave the second poorest bleed out of the five methods used. Apparently, the results of these studies indicate that some slaughter methods are experimentally more effective than others under certain circumstances, however, these may not always produce the greatest bleed out. Therefore, the superiority of any one method and its exclusive use in the processing plants may be questionable. In reviewing the research results on poultry slaughter methods, Heath (1984) states "Some of the research results from which poultry slaughter methods were developed were wrong. Because of this, only about one third of broiler chickens are stunned in stunners as they are used today; the others are either killed outright or not stunned sufficiently. Although dead birds bleed slightly more slowly than stunned birds during the first 90 seconds after venesection, there is no difference between blood losses of the two groups after 180 seconds. Different amounts of blood left in the carcass make no detectable difference to the carcasses, and the amount of blood left in the carcass does not affect the keeping quality. It is suggested that this lack of correlation between blood draining from the carcass and the quality of the carcass may be because the capillary bed of the muscles does not lose any blood-- all the blood coming from the neck may be from viscera and large blood vessels. These findings indicate that all birds should be killed in the stunner, thus preventing the cruelty which is associated with present methods of slaughter" (pp.157-158). The U.S. Standards of quality and grades for poultry are used extensively for grading purposes. The basic reason for grading is to classify the products according to economic value. The factors affecting product grade include body conformation, fleshing, fat cover, deformities, flesh and 24 skin bruises and such dressing defects as pinfeathers, disjointed or broken bones, missing parts, discolorations, poor bleeding, tears, cuts and abrasions (Brant et al., 1982).' 2.7 Meat Yield of Poultry The percentage of dressed carcass weight to live body weight is often used as a measurement of meat production in farm animals. Although eviscerated poultry carcasses are not completely comparable with the dressed carcasses of other kinds of livestock, a study of the relationship between eviscerated and other bodyweights can be of aid in the estimation of meat production in poultry (McNally and Spicknall, 1949). Many workers have reported data dealing with dressed and eviscerated yields of broilers. In these reports by Lowe (1941); Jull et al. (1943); Essary et al. (1951); and Jaap et al. (1950), the dressed yields varied from 85% to 90% of live weight and eviscerated yields varied from 65% to 75% of live weight. Several reports are available regarding the various factors affecting meat yield of poultry. The meat yields from live, dressed, and eviscerated Rhode Island Red cockerels were reported by McNally and Spicknall (1949). They slaughtered 183 birds at varying ages (25 biweekly intervals) with liveweights varying from 600 to 2700 grams. In their data covering this wide range of age and size, it was observed that the percentage dressed and eviscerated 25 yields, as well as edible flesh, became greater as live body weight increased. The relationship was linear and was accurately predictable from regression formulae. Studies were also conducted by several workers to determine the effects of strains and crosses on yields of eviscerated (ready-to-cook)'poultry. Renard (1949) noted considerable variation among breeds and crosses with regard to loss during dressing both from live to New York dressed and from live to eviscerated weights. Hathaway et al. (1953) found no significant difference between strains as to percentage loss from live to New York dressed weights. However, they did find a difference between strains with the Dark CorniSh yielding the highest percentage of total edible meat based on both live and on eviscerated weights. Frischknecht and Jull (1946) observed the same results in their studies with 12 week old chickens. In all trials, the Dark Cornish, yielded the highest percentage of total edible meat and breast meat on the basis of live weight and also eviscerated weight. Orr (1955) reported no significant effect of strains, sex and diet on chilled dressed weight as a percentage of live weight. However, on the basis of ready-to-cook weight as a percentage of live weight, the effect of strain and sex was highly significant with White Cornish giving the highest yield. Reports by Stotts and Darrow (1953) indicated that the introduction of Cornish breeding either in pure form or in crosses resulted in increased yields of edible meat. 26 Several conclusions about the meat yield can be drawn from these studies. Eviscerated yields vary from 65% to 75% of live weight, and these yields become greater as live body weight increases. Also, the results from these trials indicated that certain strains and crosses differ in the yields of eviscerated weights when expressed as a percentage of live weight. In other words, strains have a significant effect on eviscerated weight as a percentage of live weight. Contradictory results, however, are reported regarding the effects of strains on the yields of dressed weight. Hathway et al. (1953) and Orr (1955) observed no significant difference between strains, but Renard (1949) reported a significant variation among strains with New York dressed weights when expressed as a percentage of live weight. CHAPTER 3 METHODOLOGY 3.1 Experimental Design To determine the effects of different dietary protein levels and rearing methods on the performances of cornish game hens and broilers, a 4 x 2 factorial arrangement of treatments were involved with four levels of dietary protein (20%, 22%, 24%, and 26%), and two rearing methods (floor and cage housing). Treatments involved were composed of 8 possible combinations of 2 factors, each combination having 4 replicates (Table 1). The duration of the experiments was six weeks, initiated on April 3, 1990 and terminated on May 15, 1990. 3.2 Experimental Diets An attempt was made to evaluate further the protein levels required for optimum performance of cornish game hens and broilers. The formula and chemical composition of experimental rearing rations during 0-3 week and 3-6 week periods are offered in Tables 2 and 3, respectively. For the first 3 weeks, all chicks were given diets containing approximately 1.0% of calcium and 0.45% of phosphorus (Table 2). From 4 to 6 weeks of age, the birds were provided with 27 28 their respective diets containing approximately 0.9% of calcium and 0.4% of phosphorus (Table 3). Table 1. Experimental design for cornish game hens and broiler chicks Floor Cage Period Protein(%) Protein(%) Cornish game hens (0_4 wks) 20 22 24 26 20 22 24 26 Broilers 20 22 24 26 20 22 24 26 (0-6 wks) No. of replicates 4 4 4 4 4 4 4 No.of 10 10 10 10 10 10 10 10 chicks/replicate 259 Table 2. Formula and chemical composition of experimental rearing rations during 0-3 week period Protein levels 20% 22% 24% 26% Ingredients lbs lbs lbs lbs Corn, yellow 663 596 523 451 Wheat grain 663 589 521 453 Soybean meal 513 635 756 877 (44%) Fishmeal(60.5%) 80 80 80 80 Fat(animal-veg.) 20 40 60 80 Dicalcium phosphate 27 26 25 23 Limestone, ground 22 . 22 23 24 Salt 5 5 S 5 Methionine 2 2 2 2 Vit.-minera1 premix 5 s 5 5 Totals (lbs) 2000 2000 2000 2000 Calculated analysis Crude protein(%) 20.01 22.01 24.01 26.00 Crude fat(%) 3.44 4.29 5.14 6.00 Crude fiber(%) 3.42 3.71 3.99 4.27 Calcium(%) 1.01 1.01 1.03 1.05 Avail. phosphorus 0.45 0.45 0.45 0.44 ms* (kcal/kg) 2913 2908 2895 2889 Calorie: . . protein 145.58 132.14 120.58 111.1 * Metabolizable Energy 3() Table 3. Formula and chemical composition of experimental rearing rations during 3-6 week period Protein levels 20% 22% 24% 26% Ingredients lbs lbs lbs lbs Corn, yellow 665 601 526 454 Wheat grain 664 587 522 454 Soybean meal 513 635 756 877 (44%) Fishmeal(60.5%) 80 80 80 80 Fat(animal-veg.) 20 40 60 80 Dicalcium ‘ phosphate 21 20 19 19 Limestone, ground 20 20 20 19 Salt 7 7 7 7 Methionine 7 7 7 7 Vit.-mineral premix 3 3 3 3 Totals (lbs) 2000 2000 2000 2000 Calculated analysis Crude protein(%) 20.03 22.02 24.02 26.03 Crude fat (%) 3.44 4.29 5.15 6.00 Crude fiber(%) 3.43 3.71 3.99 4.27 Calcium (%) 0.91 0.91 0.91 0.91 Avail. phosphorus 0.40 0.40 0.40 0.41 ME* (kcal/kg) 2917 2913 2904 2897 Calorie: protein 145.64 132.28 120.90 111.31 * Metabolizable Energy 31 3.3 Methods of Experiment A total of 320 one-day old cornish game hen/broiler pullets from a commercial hatchery was used in this experiment. Ten chicks were randomly alloted to each of the 16 floor pens (10 x 7.5 sq. ft.) and 16 cage units (2 x 3 sq. ft., 1.8 ft. high) after recording their average body weights. The cage units compriSed two 4-tier cage arrangements with 2 cages per tier. Wood shavings were used as litter for floor pens. Room temperature ranged from 78° F to 80° F. Both feed and water were available ad libitum throughout the experimental period. Birds that died in the cage or floor system during the first three days were replaced. After three days mortality was recorded as it occurred. Data on weight gain were recorded at 3, 4, 5 and 6 weeks of age. Feed consumption was recorded over the 0-4 and 0-6 week periods, and feed conversion was calculated as the unit weight of feed per unit body weight. At 4 and 5 weeks of age, three chicks per replicate were randomly selected for slaughter. At the end of the experiment, remaining broilers from each replicate were slaughtered. The birds chosen for slaughter were leg-banded to permit individual identification at all weighings and upon carcass evaluation after slaughter. Prior to slaughter, the chickens were kept in wooden crates overnight. On the following morning the chicks were taken out of the crates, and suspended by their hocks from shackles of an 32 overhead conveyor. Approximately half of the birds were stunned by electric shock and killed by conventional method (single carotid artery and jugular vein cutting). The rest of the chickens were not stunned and killed by cervical dislocation method. Care had been exercised to obtain a thorough bleeding before the birds entered the scalding tank. The feathers were removed after semi-scalding (at 125° F, 7 rotations for cornish game hens and 15 rotations for broilers) by the use of a mechanical picker. Defeathered birds were then hung by their feet on the evisceration line from an overhead conveyor, which moved the carcasses through the eviscerating area. Evisceration was performed as uniformly as possible with several people doing the work. The carcasses were eviscerated by cutting them open down the back on one side of the vertebral column. The neck with skin was cut off at its base and the shanks were removed at the hooks. The respiratory organs, reproductive organs, liver, gizzard, intestines and heart were removed. Care was taken to retain abdominal fat during removal of these organs for further determination of abdominal fat-weight. As soon as the birds were eviscerated, they were plunged into cold water directly from the eviscerating line for chilling and left there for two or three hours. After Chilling, the carcasses were hung on the drip line to permit the carcasses to drain adequately before they were graded and Weighed. 33 The eviscerated carcass weights (giblets not included) were then recorded. Factors affecting product quality included appearance (skin color with regards to degree of bleeding), body conformation (structure or shape of carcass), fleshing (covering of flesh) and finish (layer of fat in the skin). Each eviscerated carcass was then classified according to USDA standards as A, B and C (Table 4). The data were then used to calculate the percentage of Grade A carcasses originating from each dietary protein level. Carcasses down-graded because of breast blisters were also listed and these data were used to calculate the incidence of breast blisters. The scoring system used for evaluating breast blistering in cornish game hens and broilers is presented in Table 5. The birds which were graded A were considered to have had very slight blisters or no bliSters. Table 4. Scoring system@ for grading carcasses in cornish game hens and broilers Score Grade 86-100 A 75-85 B 60-74 . C av‘°T’he grading of carcasses and eValuation of breast blisters (Tables 4 & 5) were based on the scoring system suggested by Dr. Larry Dawson, Michigan State University, East Lansing, Michigan. 34- Table 5. Scoring systemP for evaluating blisters in cornish game hens and broilers Score Grade 86-100 At 75-85 BH 60-74 Cm 1’ No blisters or very slight blisters ; H Blisters, moderate; T” Blisters, severe The adipose tissue known as gizzard fat was then removed. This layer of fat surrounded the gizzard and lay between the abdominal muscles and intestines. Another layer of adipose tissue known as leaf fat was also removed. This layer extended within the ischium, and surrounded the bursa of Fabricius and cloaca, where it was attached to the abdominal muscles in the area of the bursa of Fabricius. Both gizzard and leaf fats constituted the abdominal fat and their weights were recorded. 3.4 Analysis of Data Both descriptive and inferential statistics were employed in the analyses of these data. The descriptive statistics were primarily means, standard deviations, percentages and frequency distribution of performance data. Correlation analysis, an inferential statistics was performed to measure the strength of the relationship between live body weight and incidence of breast blisters, between 35 live body weight and percent abdominal fat weight, and between live body weight and percent eviscerated weight. Before statistical analyses, percentages were subjected to arcsine transformation. Chi-square distribution was used to test the null hypothesis that the carcass appearance and slaughter methods are independent. The treatment main effects and their interactions were determined by using the general linear model (GLM) procedure of SAS. The experimental unit used to analyze the data was the pen average for each variable. The following statistical model was used for analysis of variance of average live weight, feed consumption and feed conversion. Yijk = u, + Pi + Rj + (PR)j_j + Eijk vmere: Yijk = a typical observation; p, = the overall mean; Pi = an effect due to protein levels with i = 1, 2, 3, 4; Rj = an effect due to rearing with j = 1, 2; PRij = the interaction between the main effects; k = 1, 2, 3, 4 pens per treatment; and Eijk = the residual. Another statistical model was used in the analysis of carcass grading, which is as follows 236 Yijkl = 114+ Pi + Rj + Ak + (PR)ij + (PA)ik + (RA)jk + (PRA)ijk + Eijkl where: Yijkl = a typical observation; “- = the overall mean; Pi = an effect due to protein levels with i = 1, 2, 3, 4; Rj = an effect due to rearing with j = 1, 2; ‘, Ak = an effect due to age with k = 1, 2, 3; PRij = the interaction protein level * rearing; PAik = the interaction protein level * age; RAjk = the interaction rearing * age; PRAijk = the interaction protein level * rearing * age; 1 = 1, 2, 3, 4 pens per treatment; and Eijkl = the residual. All statistical analyses of data were performed using the Statistical Analysis System (SAS Institute Inc., 1988). CHAPTER 4 RESULTS AND DISCUSSION 4.1 Influence of Different Protein Levels on the Performance of Floor- and Cage-Reared Cornish ‘Game Hens and Broilers 4.1.1 Cornish Game Hens: The averages of the final body weights, feed consumption and feed efficiencies of cage- and floor-housed cornish game hens fed on four different levels of dietary protein from 0-4 weeks of age are summarized in Table 6. No statistically significant differences were observed for 4-week live body weights among the cage- and floor-reared birds, although the body weights of the floor—reared birds averaged 0.1 kg. more than the cage-reared birds. In cage- reared cornish game hens, the groups of birds that were offered the 20%, 24% and 26% dietary protein gained significantly more weight than the group of birds offered the diet containing 22% protein. In floor-reared birds, the differences in body weight were nonsignificant due to variable levels of protein. During the 0-4 week experimental period, nonsignificant differences were observed for feed consumption among the cage- and floor-reared cornish game hens. In cage rearing 37 38 system, the groups of cornish game hens that were given a diet with 20% protein consumed significantly more feed than did the birds that were offered the diet containing 22% or 26% protein. The birds which were offered a 24% protein diet also consumed more feed during this period than those 'receiving a 22% protein diet (P<.05). In floor-reared cornish game hens, the group of birds that was given a diet imith 26% protein consumed significantly less feed than those that received 22% or 24% dietary protein. unable 6. Effects of protein levels on the performance of cage and floor reared cornish game hens Rearing system ¥ Protein level Response criterion (96) , Cage Floor Lisve weight, kg 20 0.973a 0.995a ' 22 0.817b 1.0283b 24 0.9344cd 1.0384:llDC 26 0.9514(1 1.016abc Avg. rearing 0.919 1.019 system Feed consumption 20 1.781a 1.5993 Per bird, kg 22 1.4081001 1.618ab 24 1.81536 1.6543“ 26 1.521cd 1.5498(1 Avg. rearing 1.631 1.605 system Feed efficiency, 20 1.8283 1.618a feed/gain. kg/kg 22 1.725bo 1.583abd 24 1.945ac 1.593abc 26 1.615“ 1.530alccl Avg. rearing 1.778 1.581 \ system NCfte: Within columns, means with different superscripts are 81gnificantly different (P<.05) . 39 Nonsignificant differences were observed for feed efficiency among cage- and floor-reared units. For cage- reared cornish game hens, the best feed/gain relationship was obtained by the group of birds that received a 26% protein diet. Statistically (P<.05) this feed efficiency did not differ from the group of birds offered the diet containing 22% protein, but was significantly different than the birds offered 20% or 24% dietary protein. In floor-reared birds, the differences in feed efficiency were nonsignificant due to variable protein levels. 4.1.2 Broilers: The effects of protein level and cage vs. floor rearing on the performance of broilers (0-6 weeks) are summarized in Table 7. At the end of the 6 week experimental period, the average body weight of cage-reared broilers was found to be the same as the floor-reared broilers. When comparisons were made among different dietary treatment, the 22% protein diet produced the lowest average body weight in cage-reared broilers (P<.05). In floor-reared broilers, the differences were found to be nonsignificant for 6-week live weights due to variable levels of protein. Broilers reared on the floor consumed 0.159 kg. more feed per bird than did the comparable broilers in cages, however, nonsignificant differences were observed for feed 4() consumption among the cage- and floor- reared broilers. Cage-housed broilers fed on diet containing 20% protein consumed more feed than those fed on diets with 24% or 26% protein (P<.05). Floor-reared broilers offered a diet containing 26% protein consumed significantly less feed than those receiving 20% or 24% protein diet. Table 7. Effects of protein levels on the performance of cage and floor reared broilers Rearing system Protein level Response criterion (%) Cage Floor Live weight, kg 20 1.767a 1.706a 22 1.523b 1.676ab 24 1.698ac 1.694abc 26 1.7isacd 1.629abc Avg. rearing 1.676 1.676 system Feed consumption 20 3.458a 3.4453 per bird. kg 22 2.785b 3.347abd 24 3.327abc 3.414ab 26 3.242cd 3.241d Avg. rearing 3.203 3.362 system Feed efficiency 20 1.9643 2.018a feed/gain, kg/kg' 22 1.963abd 2.000abd 24 1.998abc 2.017abc 26 1.883acd 1.991d Avg. rearing 1.952 2.007 system ' Note: Within columns, means with different superscripts are significantly different (P<.05). 41 No statistically significant differences were observed for feed efficiency among the cage- and floor—reared broilers. Andrews and Goodwin (1973) also reported nonsignificant differences among the cage- and floor-housed broilers for feed efficiency. Floor-housed birds offered a diet with 26% protein were significantly more efficient in the utilization of feed compared to broilers fed diets with 20% or 24% protein. In cage-reared broilers, however, the differences in feed efficiency were nonsignificant among different dietary treatments. The analyses of variance of average body weight, feed consumption and feed efficiency were performed. The data from both cornish game hen and broiler experiments were pooled for statistical analysis. Table 8 shows the mean squares of analyses of variance of performance data. The present result, in which dietary protein had no significant effects on live weight, are in general agreement with other studies. Summers and Leeson (1985) reported that crude protein level had little influence on male broiler body weight gain during the 28 to 49-day period. Lilburn et al. (1987) also recorded nonsignificant differences in body weight that were due to variable levels of protein. In contrast to the result of the present study, Pesti and Fletcher (1983) reported that broiler growth increases with increasing dietary protein content. They also found food consumption to be dependent on dietary protein content. 42 No significant effects on live weight and feed consumption were noted that were due to rearing (Table 8). This observation supports Andrews and Goodwin (1973) who found no significant differences for 8eweek live body weights among the floor and cage units. Table 8. Analyses of variance of average body weight, feed consumption and feed efficiency Mean squares Source DF weighfifkg) consumH:?::(kg) efff:?::cy protein (2) 3 0.140 1.536 0.290* Rearing (R) 1 0.349 0.083 0.781** P—x R 3 0.183 1.166 0.066 Residual 24 '0.057 0.874 0.447 *PS. 001; **PS. 0001 . The analyses of variance showed that protein and rearing effects were highly significant for feed efficiency. In cage-reared cornish game hens and floor-housed broilers, the groups which consumed 20% or 24% protein diet required a greater quantity of feed to achieve the same body weight as the birds that were fed the 26% protein ration (Tables 6 & 7). Support for this observation is given by several workers who demonstrated better feed utilization in chicks with increasing dietary protein content (Donaldson et al., 1956; Eberst et al., 1972; Gowda, 1973; Leong et al., 1959; Pesti 43 and Fletcher, 1983; Prasad et al., 1973; Rao et al., 1973), however, optimal feed efficiency has been obtained with broiler grower diets containing as little as 15.5% crude protein (Lipstein and Bornstein, 1975; Summers and Leeson, 1985). The protein level x rearing interaction was not statistically significant for any of these parameters measured (Table 8). 4.2 Effects of Dietary Protein Levels and Cage Vs. Floor Rearing on Carcass Grading 4 4.2.1 Cornish Game Hens: ' Carcass quality is an important consideration because of the further processing used by the industry. In this study, the primary components which together comprise overall carcass quality (i.e., appearance, conformation, fleshing, finish and blisters) were evaluated. Table IX (see Appendix) lists the percentages of cornish game hen carcasses graded into different grade classes according to the protein level fed and the method of rearing. In cage-reared cornish game hens, the group that were offered a diet containing 20% protein yielded highest percentages of Grade A carcasses than did the comparable groups fed diets with 22%, 24% or 26% protein (P<.005). 4.2.2 Broilers: The results obtained with the study to determine the effects of different protein levels and rearing on carcass 44 grading in cage- and floor-reared broilers at 5 and 6 weeks of age are presented in Tables X & XI (see Appendix). When comparisons were made among different dietary treatments, diet with 26% protein yielded the highest percentages of Grade A carcasses in cage-housed broilers at 6 weeks of age (P<.025). However, this percentage yield may be influenced by the small size of the sample (see Table XI). In floor- reared broilers at 6 weeks of age and also in cage-grown loroilers at both 5 and 6 weeks of age, nonsignificant (differences were observed in Grade A carcasses that were due 1:0 different levels of dietary protein. Tables 9 & 10 present the combined data of carcass grading (pooled from cornish game hens and broiler experiments) by rearing and protein levels, respectively. The mean squares of analyses of variance of these data are stuown in Table 11. Level of dietary protein, age, rearing arud their interactions were the effects tested. Except for appearance grade, the effects of rearing were found to be highly significant for all other components of grading (P.05) for any of the quality factor evaluated except for appearance (P<.01). The age x rearing interactions were found to be significant for finish and blisters (P<.05), and highly significant for appearance (P<.01). The second order interactions, age x protein level x'rearing were highly significant for appearance (P<.001) and blisters (P<.01), but were significant for conformation and finish grades (P<.05). No other literature were available to the author to support or disagree with the findings of the present study on carcass grading. Table 11. Analyses of variance of carcass grading in cornish game hens and broilers Mean squares Source DF Appearance Conformation Fleshing Finish Blisters Age(A) 2 4.3 54.4 56.3 37.2* 158.5*** Protein(P) 3 231.1** 57.5* 48.6 78.2*** 86.4** Rearing(R) 1 2.7 2378.4*** 1225.4*** 29l.3*** 4999.9*** A x P 6 217.4** 34.3 11.3 25.7* 68.3** P x R 3 296.7** 23.0 11.2 24.9 19.3 A x R 2 412.3** 11.4 27.9 48.9* 91.4* A x p x p. 6 238.9*** 43.6* ' 4.3 24.74 . 64.4“ Residual 69 62.2 20.9 22.2 19.5 17.1 ‘P<.05; **p<.01; ***p<.001. 48 4.3 Breast Blistering in Cornish Game Hens and Broilers 4.3.1 Cornish Game Hens: To compare the incidence of breast blisters between cage- and floor-reared cornish game hens, the data from all four dietary treatments under each rearing method were pooled for statistical analysis. The scoring system used for evaluating breast blistering in cornish game hens is presented in Table 5. The results in Table 12 show that breast blisters were present in 30.23% of the cage birds examined. No incidence of blisters was reported in cornish game hens reared on the floor. Table 12. Breast blisters incidents in cornish game hens, by Rearing system Rearing system Blisters (%) No Blisters (%) Total Cage (13) 30.23 (30) 69.77 (43) 100.00 Floor (0) 0.00 (46) 100.00 (46) 100.00 Total (13) 14.61 (76) 85.39 (89) 100.00 Note: Figures in parentheses are base NS for the adjacent percentages. Correlation coefficients between live body weight and breast blisters were determined for each rearing method (Table 13). The values, r= -0.l74 and -0.l68 for cage- and 49 floor-reared birds, respectively were found to be non- significant (P<.05). Table 13. Correlation coefficients between live weight and breast blisters in cornish game hens Rearing Correlation coefficient Significance system (r) Cage (43)§ —0 174 NS Floor (46) -0.168 NS NS, non-significant: §LFigures in parentheses are base Ns for the adjacent correlation coefficients. 4.3.2 Broilers: I The percentages of broilers having breast blisters reared in cages or on floor for 5 and 6 weeks are presented in Table 14. The scoring system used for evaluating blisters in broilers was the same as used for cornish game hens (see Table 5). For each rearing method at each age, the data from all four dietary treatments were pooled for analysis. At 5 weeks of age, 31.11% of the broilers reared in cages were reported to have breast blisters compared to only 2.50% of the broilers reared on floor. At 6 weeks of age, 71.43% of broilers raised in cages had breast blisters, a value within the percentage range reported by Welch et al. (1970). These researchers found breast blisters to be 68% to 91% on broilers reared on wire floors in cages. No blisters 5() were detected on broilers reared on the floor for 6 weeks. These findings support Andrews et al. (1990) who reported that litter-grown broilers had few or no breast blisters. Table 14. Breast blister incidents in broilers, by Age and Rearing Age(wks) Rearing Blisters No Blisters Total system (%) (%) 5 Cage (14) 31.11 (31) 68.89 (45) 100.00 Floor (1) 2.50 (39) 97.50 (40) 100.00 6 Cage (30) 71.43 (12) 28.57 (42) 100.00 Floor (0) 0.00 (59) 100.00 (59) 100.00 Total (45) 24.19 (141) 75.81 (186) 100.00 Note: Figures in parentheses are base Ns for the adjacent percentages. Table 15 lists the correlation coefficients between live weight and incidence of breast blisters in broilers by age and rearing method. The only highly significant negative correlation (P<.01) was that observed between live weight and breast blister incidence in cage-reared broilers at 5 weeks of age (r= -0.369). The results in Tables 13 & 15 therefore indicate that in this study live weight was not the determining factor influencing the extent of breast blistering in both cornish game hens and broilers. Also correlation coefficients were extremely small and thus, these relationships are likely to be of little practical importance. These observations, 51 however, are not in agreement with other studies reported. Welch et a1. (1970) found breast blistering to be significantly correlated with body weight. Smith (1956) and Andrews (1972) also observed a tendency for heavier birds to have more blisters. Table 15. Correlation coefficients between live weight and breast blisters in broilers, by Age and Rearing Age Rearing Correlation (wks) system coefficient (r) Significance 5 Cage (45)§ -0.369 * Floor (40) 0.176 NS 6 Cage (42) -0.173 NS Floor (59) -O.109 NS *P<.01; NS, non-significant; 5Figures in parentheses are base Ns for the adjacent correlation coefficients. 4.4 Correlation between Live Weight and Abdominal Fat (Expressed as a Percentage of Live Weight) in Cornish Game Hens and Broilers 4.4.1 Cornish Game Hens: The means and standard deviations for percent abdominal fat on a live weight basis are preSented in Table 16 by protein level and rearing method. Results show that abdominal fat expressed as a percentage of live weight ranged \ from 0.82% to 1.40%. Abdominal fat contributed to a maximum 52 of 1.40% to the total live weight in cornish game hens reared in cages and a maximum of 1.29% to the total live weight in birds reared on the floor. Among the cage—reared cornish game hens, highest percentage of abdominal fat was produced by those that were fed diet containing 20% protein. Floor- reared birds fed a diet containing 22% protein gave the highest percentage of abdominal fat. With the exception of floor-reared cornish game hens that were given a diet with 20% protein, percent abdominal fat decreased linearly with increasing dietary protein. These results agree with the previous report which indicated that abdominal fat deposition, as a percentage of whole body weight decreased linearly as dietary crude protein content increased (Fancher and Jensen, 1989). Svensson and Hakansson (1977) also reported that chicks fed low protein diets have a high content of abdominal fat. No significant differences were observed among cage- and floor-reared cornish game hens for percent abdominal fat. Table 17 presents the correlation coefficients between percent abdominal fat and live weight by protein level and rearing method in cornish game hens. Correlation coefficients between these parameters ranged from r= -O.239 to +0.567, and from r= -0.255 to +0.501 in cage- and floor— reared birds, respectively. Results in Table 17 revealed that the correlation between percent abdominal fat and live weight were very low except for the groups that were reared in cages and offered the diets containing 20% or 24% protein 53 (P<.10), and also for those floor-reared birds that were given a diet with 22% protein (P<.10). No significant correlations (P<.05) were obtained for percent abdominal fat and live weight in either cage- or floor-reared cornish game hens for any dietary protein levels. This suggests that live weight has little or no relationship with the deposition of abdominal fat at this relatively early age (4 weeks). An alternate explanation could be that sample size was not adequate to demonstrate meaningful correlations between these parameters. Again, factors other than growth rate could be involved with this abdominal fat deposition. Table 16. Means and standard deviations of abdominal fat‘ in cornish game hens Cage Floor Protein 4.. levelj%)i N Mean(%) SD(i) N Mean(%) SD(_) 20 11 1.40 0.383 12 0.96 0.531 22 8 1.19 0.789 10 1.29 0.409 24 11 1.16 0.392 12 1.20 0.275 26 11 0.82 0.198 12 0.94 0.497 Average 1.14a 1.10a * Arcsine percentage transformation for abdominal fat expressed as a percentage of body weight; a Means with same superscripts are nonsignificant. 541 Table 17. Correlation between live weight and abdominal fat (expressed as a percentage of live weight) in cornish game hens Protein Rearing Correlation , , , _l§vel(%) system coefficient(r) Significance 20 Cage (11)5 0.567 NS Floor (12) 0.159 NS 22 Cage (8) 0.261 NS Floor (10) 0.501 NS 24 Cage (11) 0.531 NS Floor (12) -0.255 NS 26 Cage (11) -0.239 NS Floor (12) 0.099 NS NS, non-significant; §iFigures in parentheses are base Me for the adjacent correlation coefficients. 4.4.2 Broilers: The means and associated standard deviations for abdominal fat on a percent of body weight basis are shown in Table 18 by protein levels, age and rearing method. At 5 and 6 weeks, nonsignificant differences were observed cage and floor-housed broilers. Contrary to the result the present study, Deaton et al. (1974) observed larger quantities of abdominal fat in broilers reared in cages compared to broilers reared on the floor. both among of when When comparisons were made within each rearing method at 5 and 6 weeks, both cage and floor broilers showed 55 inconsistency in the percentages of abdominal fat. For unknown reasons, at 5 week of age the cage-reared broilers consuming 20% and 22% protein diet had a larger percentage of abdominal fat than the 6-week old broilers reared under the same condition. Similarly 5-week old broilers reared on the floor and fed 22% and 26% dietary protein had greater quantities of abdominal fat when expressed as a percentage of live weight than 6-week old broilers. The author has no explanation for the reduction in abdominal fat deposition except to attribute these anomalies to variation in sample size. Table 18. Means and standard deviations of abdominal fat* in broilers . Cage Floor Pi???“ <33; N ff. . “5:,“ if. 20 5 11 1.75 0.356 8 1.45 0.469 22 12 1.59 0.562 11 1.71 0.342 24 12 0.98 0.307 11 0.96 0.362 26 11 1.22 0.368 10 1.07 0.543 Average 1.38a 1.30a 20 6 15 1.46 0.529 15 1.56 0.554 22 12 1.36 0.483 16 1.50 0.503 24 13 1.53 0.470 15 1.46 0.608 26 2 1.75 0.051 13 0.90 0.459 .Average 1.52a 1.36a * Arcsine percentage transformation for abdominal fat expressed as a percentage of body weight; a Within age, means with same superscripts are nonsignificant. 56 The correlation coefficients between percent abdominal fat and live weight are presented by protein level and rearing method in Table 19. The highest correlation coefficients obtained were r= +0.514 for cage-housed broilers and r= +0.795 for broilers raised on the floor. Except for the group of 6-week old broilers that were reared on the floor and fed the 22% protein diet (PS.0002), the relationship of percent abdominal fat with 5- and 6-week body weight was low and nonsignificant in both cage- and floorv reared broilers for all dietary protein levels. Failure to show meaningful correlations between percent abdominal fat and live weight suggests that body weight has little or no effect on abdominal fat development. This finding agrees with the report of Middelkoop et al. (1976). These workers used 45-day old hybrid broilers and found that the variation in growth rate had no relationship with the percentage of abdominal fat. Factors other than live weight may be involved with this fat deposition. Summers and Leeson (1979) indicated that energy intake is the main factor that influences abdominal fat deposition. In addition, environmental factors such as the season of the year and the temperature may exert some influence on feed intake and subsequent fat deposition in broilers (Kubena et al., 1972). Contrary to the result of the present study, Sonaiya and Benyi (1983) found a highly significant (P<.Ol) correlation between live weight and percent abdominal fat in broilers, 57' but their studies dealt with later stages of growth (>6 weeks). Table 19. Correlation between live weight and abdominal fat (expressed as a percentage of live weight) in broilers Cage Floor Protein Age Correlation Signif— Correlation Signif- level(%) (wks) coefficient icance coefficient icance (r) (r) 20 5 (11)§ -0.123 NS (8) 0.088 NS 22 (12) 0.455 NS (11) -0.008 NS 24 (12) -0.001 NS (11) -0.224 NS 26 (11) 0.440 NS (10) 0.043 NS 20 6 (15) -0.466 NS (15) -0.031 NS 22 . (12) 0.150 NS (16) 0.795 * 24 (13) 0.514 . NS (15) -0.127 NS 26 (2) -1.000 - (13) -0.036 NS NS, non-significant; *PS.0002; §Figures in parentheses are base Ms for the adjacent correlation coefficients. 4.5 Correlation between Live Weight and Eviscerated Weight (Expressed as a Percentage of Live Weight) in Cornish Game Hens and Broilers 4.5.1 Cornish Game Hens: The means and standard deviations for eviscerated weight expressed as a percent of live weight are given in Table 20 by protein level and rearing method. The highest 58 eviscerated weight of the birds obtained was 66.63% of live weight. No statistically significant differences were observed for percent eviscerated weight among cage- and floor-reared cornish game hens, although the eviscerated weights of floor-reared birds ranged from 0.08% to 3.41% higher. Table 20. Means and standard deviations of eviscerated weight* in cornish game hens Cage Floor Piggzin N Mean SD N Mean so (%) (%) (i) (%) (i) 20 11 65.66 2.37 12 66.63 3.34 22 8 64.19 3.53 10 , 63.74 8.00 24 11 62.75 2.39 12 66.16 1.58 26 12 66.14 9.84 12 66.22 1.72 Average 64.69a 65.69a * Arcsine percentage transformation for eviscerated weight expressed as a percentage of body weight; a Means with same superscripts are nonsignificant. The correlation coefficients between percent eviscerated weight and live body weight for each protein level and rearing method are presented in Table 21. The correlation coefficients obtained ranged from -0.192 to +0.475 in cage-reared cornish game hens and from -0.052 to +0.386 in floor-reared birds. Percent eviscerated weight had .59 non-significant correlations to live weight in both cage and floor-reared cornish game hens (Table 21). Table 21. Correlation between live weight and eviscerated weight (expressed as a percentage of live weight) in cornish game hens Protein Rearing Correlation Significance evel(%) system coeff1c1ent(r) 20 Cage (11)§ 0.475 NS Floor (12) 0.386 NS 22 Cage (8) 0.021 NS ' Floor (10) -0.064 NS 24 Cage (11) 0.449 NS Floor (12) 0.132 NS 26 Cage (12) -0.192 NS Floor (12) -0.052 NS NS, non-significant; §‘Figures in parentheses are base NS for the adjacent correlation coefficients. 4.5.2 Broilers: Table 22 presents the means and standard deviations for percent eviscerated weight on a live weight basis by protein level, age and rearing method. The highest eviscerated weight obtained was 72.51% of live weight for floor-reared broilers and 66.98% for the broilers in cages. In a report by Hathway et al. (1953), the eviscerated yields ranged from 68.3% to 73.4% of live weight in broilers. Their studies, however, dealt with 12—week old broilers of different breeds. 6() When comparisons were made among rearing methods, nonsignificant differences were observed for percent eviscerated weight at both 5 and 6 weeks of age (Table 22). Table 22: Means and standard deviations of eviscerated weight* in broilers Cage Floor Protein. level Age N Mean SD N Mean SD, (%) (wks) (%) (i) (%) (i) 20 5 11 66.12 7.78 8 72.51 1.50 22 12 66.35 3.09 11 67.84 2.78 24 12 65.02 2.62 11 67.31 2.63 26 11 63.49 3.04. 10 66.12 3.28 Average 65.25a 68.45a 20 6 15 66.70 5.91 15 67.94 2.50 22 12 64.84 3.11 16 67.99 2.61 24 13 66.88 3.36 15 66.67 . 2.38 26 2 66.98 1.40 13 65.84 2.97 Average 66.35a 67.11a * Arcsine percentage transformation for eviscerated weight expressed as a percentage of body weight; ‘ a Within age, means with same superscripts are nonsignificant. The correlation coefficients between percent eviscerated weight and live weight in broilers are shown in Table 23. Nonsignificant correlations were observed between percent eviscerated weight and live weight for cage-reared broilers at 5 and 6 weeks of age. Floor-reared broilers, however, had correlation coefficients significantly different 61 from zero at the 1% level of probability for 20% protein (fifth week) and at the 5% level of probability for 24% and 26% protein (sixth week). Similar findings were reported by McNally and Spicknall (1949) who in their studies observed that the percentage of eviscerated yields became greater as live body weight increased. Jaap et al. (1950) also reported a linear relationship between live weight and percentage eviscerated yields. Table 23. Correlation between live weight and eviscerated weight (expressed as a percentage of live weight) in broilers Cage Floor Protein Age Correlation Signif- Correlation Signif- level (wks) coefficient icance coefficient icance (%) - (r) (r) 20 5 (11)§ -0.375 NS (8) -0.855 ** 22 (12) -0.151 NS (11) 0.267 NS 24 (12) -0.077 NS (11) 0.198 NS 26 (11) 0.177 NS (10) -0.341 NS 20 6 (15) -0.037 NS (15) 0.189 NS 22 (12) 0.495 NS (16) -0.026 NS 24 (13) -0.391 NS (15) 0.605 * 26 . (2) 1.000 - (13) 0.565 * *P<.05; **P<.01; §iFigures in parentheses are base Ns for the adjacent correlation coefficients. 62 4.6 Effects of Slaughtering Methods by Cervical Dislocation or Conventional Method on the Appearance Grade “of Cornish Game Hens and Broilers 4.6.1 Cornish Game Hens: Table 24 lists the effects of slaughter methods on the appearance of carcasses in cornish game hens. These data reveal that in floor-reared birds, cervical dislocation yielded higher percentages (61.29%) of Grade A carcasses than did the conventional method (20.00%). In cage-grown birds, however, conventional method produced greater number (50.00%) of Grade A carcasses compared to cervical dislocation method of slaughter (26.67%). Table 24. Percentages of cornish game hen carcasses in each grade (based on appearance) for each slaughter method Rearing Cage Floor Grade Grade Slaughter method A B C A B C (%) (%) Cervical (4) 26.67 (11)73.33 (0) 0.00 (l9)6l.29 (9) 29.03 (3) 9.68 Conventional (14)50.00 (l3)46.43 (1) 3.57 (3) 20.00 (7) 46.67 (5) 33.33 Total (18)41.86 (24)55.81 (1) 2.33 (22)47.83 (l6)34.78 (8) 17.39 Note: Figures in parentheses are base Ns for the adjacent percentages. 63 4.6.2 Broilers: The percentages of broiler carcasses obtained in each grade based on appearance for each slaughter method are demonstrated in Tables 25 & 26. The data indicate that at both 5 and 6 weeks, floor-reared broilers tended to follow the same pattern as the cornish game hens. Cervical dislocation method gave better carcass grade among birds grown on floor. In cage-reared broilers, however, cervical dislocation yielded a greater percentage of Grade A carcasses at 5 weeks of age and conventional method yielded the same at 6 weeks of age. Table 25. Percentages of five-week old broiler carcasses in each grade for each slaughter method A (based on appearance) Rearing Cage Floor Slaughter Grade Grade method A B C A B C (%) (%) Cervical (5) 41.67 (6) 50.00 (1) 8.33 (20) 74.07 (7) 25.93 (0) 0.00 Conventional (7) 21.21 (22) 66.67 (4) 12.12 (2) 15.38 (8) 61.54 (3) 23.08 Total (12) 26.67 (28)62.22 (5) 11.11 (22) 55.00 (15) 37.50 (3) 7.50 Note: Figures in parentheses are base NS for the adjacent percentages. When data from cornish game hens and broilers are compiled together for comparing slaughter methods (Table 27), it appeared that cervical dislocation method produced better carcass quality in terms of appearance than did the 64 conventional method, yielding 14.41% higher of Grade A carcasses (P<.005). Table 26. Percentages of six-week old broiler carcasses in each grade for each slaughter method (based on appearance) Rearing, Cage Floor Grade Grade Slaughter method A B C A B C (%) (%) Cervical (7) 31.82 (12)54.54 (3)13.64 (l9)39.58 (23)47.92 (6)12.50 Conventional (10)50.00 (10)50.00 (0) 0.00 (4) 36.36 (7) 63.64 (0) 0.00 Total (l7)40.48 (22)52.38 (3)7.14 (23)38.98 (30)50.85 (6)10.17 Note: Figures in parentheses are base N3 for the adjacent percentages. Table 27. Effects of slaughter methods on appearance grade in cornish game hens and broilers (combined data) Grade Slaughter method A B C Total (%) Cervical (74) 47.74 (68) 43.87 (13) 8.39 (155)100.00 Conventional (40) 33.33 (67) 55.83 (13) 10.84 (120)100.00 Total (114)41.45 (135)49.09 (26) 9.45 (275)100.00 Note: Figures in parentheses are base Ns for the adjacent percentages. 65 Now the question arises whether the slaughter method accounts for all the differences observed in the percentages of carcasses in each grade based on appearance. The means employed for testing the hypothsis: carcass grading is independent of slaughter methods was the Chi—square (X2) test. The results obtained from the test are presented in Table 28. Although Brant et al. (1982) concluded that stunning was essential for satisfactory bleeding, and Newell and Shaffner (1950) indicated that bleeding enhanced carcass appearance, the result of the statistical analysis (Table 28) eliminated the influence of slaughter methods on appearance grade. The data were consistent with the hypothesis that carcass appearance and slaughter methods are independent. This observation was supported by Heath (1984) who reported that 180 seconds after venesection there is no difference between blood loss of the stunned and non—stunned groups of birds. He further stated that neither the appearance of the carcass nor its keeping quality is affected by different amounts of blood retained in the carcass. He suggested that the muscle capillaries retain their blood after slaughter while all of the bleeding may be from viscera and large blood vessels. 6(5 Table 28. Chi-square test of carcass appearance grade Statistical analysis DF Value Probability Chi-square . 2 5.787 0.055 (5.991) T 1’Tabulated values of X2 are enclosed in parentheses. Since stunning and thereafter slaughtering of birds by the conventional method showed no advantage over cervical dislocation, and since cervical dislocation, in fact, was found to produce better quality carcass, the present author believes that the feasibility of using this latter method for islaughtering in her own country could be further explored. This need is even strengthened by the fact that in rural Bangladesh electricity needed for stunning is seldom available. CHAPTER 5 SUMMARY .AND CONCLUSIONS Experiments were conducted with a total of 320 one-day old broiler chicks to determine the effects of different dietary protein levels and rearing methods on the performance and carcass quality of cornish game hens and broilers, and also the influence of slaughter methods on carcass appearance. In this study it was found that: 1. There were no statistically significant differences for live body weights, feed consumption and feed efficiency among the cage- and floor-reared cornish game hens and broilers. In cage-grown cornish game hens and broilers, the groups of birds that were given 20%, 24% or 26% dietary protein were heavier than the group of birds that received the 22% protein diet (P<.05). In cage-reared cornish game hens, and also in floor-raised broilers, the groups that fed on 26% protein diet were more efficient in the utilization of feed compared to the groups of birds offered 20% or 24% dietary protein (P<.05). Statistical examination, according to the method of analysis of variance showed no significant effects on live weight and feed consumption that were due to dietary protein level and rearing. However, on feed utilization, these effects were significant. The protein 67 68 level x rearing interaction was found non-significant for all these parameters evaluated. 2. When comparisons were made among different dietary treatments, 20% protein diet yielded highest percentages of Grade A carcasses in cornish game hens than did the comparable groups fed diets with 22%, 24% or 26% protein (P<.005). Overall, rearing chickens on floor produced better quality of carcasses compared to cage system (P<.05). In most cases the effects of age, protein level and rearing, and their interactions were found to be significant for various factors (appearance, conformation, fleshing, finish and blisters) of carcass quality. 3. Low non-significant negative correlations were observed between live body weights and incidence of breast blisters in cornish game hens and broilers with the only exception being 5-week old broilers grown in cages. In that latter group, a highly significant negative correlation coefficient was obtained between live weight and breast blisters. A total of 14.61% and 24.19% of cornish game hen and broiler chicks, respectively, had breast blisters. 4. With the exception of 6-week old broilers reared on floor and fed a 22% protein diet, nonsignificant correlations were obtained for percent abdominal fat and live body weight for all dietary protein levels in both cornish game hens and broilers. Nonsignificant differences were found for percent abdominal fat among cage- and floor-reared cornish game hens and broilers. Abdominal fat contributed to a maximum of 69 1.40% and 1.75% to total live weight in cornish game hens and broilers, respectively. For cage- and floor-reared cornish game hens, 20% and 22% protein diet yielded the highest percentages of abdominal fat respectively. Among broilers, 20% and 26% protein diet produced greater percentages of abdominal fat in cage-grown birds, whereas 22% dietary protein yielded the same in floor-raised chicks. 5. The highest eviscerated weight obtained was 66.63% of live weight for cornish game hens and 72.51% for the broilers. Correlation coefficients between percent eviscerated weight and live weight were significantly different from zero at the 1% level of probability for 20% protein (fifth week) and at the 5% level of probability for 24% and 26% protein (sixth week) in floor-reared broilers. No significant correlations were observed between these parameters in cornish game hens. 6. The cervical dislocation method of slaughter produced better carcass quality in terms of appearance than did the conventional method in cornish game hens and broilers. However, statistical analysis eliminated the influence of slaughter methods on carcass appearance. One can conclude from the results of this study that rations containing protein as low as 20% will support adequate growth and produce better carcass quality in meat- type chickens reared from day-old to 6 weeks of age. Also, when availability of space becomes a major problem for poultry operations, broilers could be grown feasibly in 70 cages. In this case, formation of blisters can be reduced by using proper flooring materials such as plastic mat or rubber covered nylon (RCN) as suggested by various workers (Lloyd, 1972; Andrews, 1972). If broilers are to be used in further processing, where breast blisters are not a major concern, these could be raised successfully in cages. Cervical dislocation could be further explored as a relatively easy method of slaughtering in commercial processing of poultry in rural Bangladesh. APPENDIX Table I. Means and standard deviations of live body weight in (0-4 weeks) cornish game hens APPENDIX Cage (N=12) FlOor (N=12) Protein Mean SD Mean SD level(%) (kg) (i) (kg) (i) 20 0.973 0.050 0.995 0.133 22 0.817 0.166 1.028 0.085 24 0.934 0.098 1.038 0.053 26 0.951 0.123 1.016 0.121 Table II. Means and standard deviations of live body weight in broilers Cage Floor Protein Age N Mean SD N Mean SD level (%) (wks) (kg) (if) (kg) (‘1); 20 5 12 1.349 0.113 12 1.308 0.112 22 12 1.180 0.171 12 1.323 0.065 24 12 1.278 0.166 -12 1.320 0.075 26 12 1.271 0.110 12 1.386 0.152 20 6 15 1.767 0.202 15 1.706 0.165 22 12 1.523 0.161 16 1.676 0.125 24 13 1.698 0.102 15 1.694 0.127 26 14 1.715 0.104 13 1.629 0.225 71 72 Table III. Means and standard deviations of cumulative feed consumption in cornish game hens (0-4 weeks) Cagejf Floor Protein Mean SD Mean SD level (%) (kg) (i) (kg) (i) 20 1.781 0.088 1.599 0.087 22 1.408 0.220 1.618 0.074 24 1.815 0.545 1.654 0.074 26 1.521 0.118 1.549 0.055 Table IV. Means and standard deviations of cumulative feed consumption in broilers Caqe Floor Protein Age Mean SD Mean SD levelw%) (wks) (kg) ‘ L;L, (kg) (:3 20 5 2.610 0.093 2.417 0.062 22 2.179 0.462 2.388 0.090 24 2.690 0.871 2.417 0.055 26 2.403 0.190 2.318 0.084 20 6 3.458 0.080 3.445 0.085 22 2.785 0.544 3.347 0.156 24 3.327 0.906 3.414 0.083 26 3.242 0.320 3.241 0.096 73 Table V. Means and standard deviations of cumulative feed conversion in cornish game hens (0-4 weeks) Cage Floor Protein Mean SD Mean SD level(%) (i) (i) 20 1.828 0.079 1.618 0.122 22 1.725 0.069 1.583 0.160 24 1.945 0.550 1.593 0.063 26 1.615 0.188 1.530 0.112 Table VI. Means and standard deviations of cumulative feed conversion in broilers Caqe Floor Protein Age Mean SD Mean SD level (%) (wks) (if) (j; 20 5 1.938 0.076 1.850 0.131 22 1.848 0.278 1.805 0.042 24 2.075 0.514 1.830 0.045 26 1.905 0.223 1.678 0.055 20 6 1.964 0.133 2.018 0.058 22 1.963 0.147 2.000 0.048 24 1.998 0.484 2.017 0.017 26 1.883 0.231 1.991 0.016 74 Table VII. Means of eviscerated(RTC) and abdominal fat(APT) weights in four-week old cornish game hens Cage Floor Protein N RTC AFT N RTC AFT level(%) (kg) ,(kg) (kg) (kg) 20 11 0.594 0.014 12 0.616 0.010 22 8 0.464 0.010 10 0.614 0.014 24 11 0.542 0.011 12 0.638 0.012 26 12 0.580 0.007 12 0.624 0.010 Table VIII. Means of eviscerated(RTC) and abdominal fat(AFT) weights in broilers Cage Floorfi Protein Age N RTC APT N RTC AFT levelgfi) (wks) (kg) (kg) (kg) (kg) 20 5 11 0.828 0.024 8 0.839 0.019 22 12 0.726 0.019 11 0.836 0.023 24 12 0.773 0.013 11 0.826 0.013 26 11 0.746 0.015 10 0.858 0 015 20 6 15 1.091 0.025 15 1.073 0.027 22 12 0.921 0.021 16 1.053 0.026 24 13 1.052 0.026 15 1.049 0.025 26 2 1.065 0.020 13 0.999 0.015 Table IX. Percentages of cornish game hen carcasses in each 75 grade, by Protein level and Rearing Protein levels 20% 22% 24% 26% Carcass quality Grade Grade Grade Grade factors A B c A s c A B c A s c Cage (%) (%) (%) (%) Appear- 72.7 27.3 0.0 22.2 77.8 0.0 36.4 54.6 9.0 33.3 66.7 0.0 ance (8) (3) (0) (2) (7) (0) (4) (6) (1) <4) (8) (0) Confor- 45.5 54.5 0.0 11.1 88.9 0.0 0.0 100.0 0.0 16.7 75.0 8.3 mation <5) (6) (0) (1) (8) (0) (0) (11) (0) <2) (9) (1) Flashing 45.5 54.5 0.0 11.1 88.9 0.0 9.1 90.9 0.0 8.3 91.7 0.0 (5) (6) (0) (1) (8) (0) (1) (10) (0) (1) (11) (0) Finish 90.9 9.1 0.0 55.6 44.4 0.0 72.7 27.3 0.0 50.0 50.0 0.0 (10) (1) <0) (5) (4) <0) (8) <3) <0) (6) (6) (0) Blisters 90.9 9.1 0.0 66.7 33.3 0.0 81.8 18.2 0.0 41.7 50.0 8.3 (10) (1) <0) (6) (3) (0) (9) (2) <0) <5) (6) (1) T 1 69.1 30.9 0.0 33.3 66.7 0.0 40.0 58.2 1.8 30.0 66.7 3.3 Ota (38) (17) (0) (15) (30) (0) (22) (32) <1) (18) (40) (2) Floor (%) (%) (%) (%) Appear- 91.7 8.3 0.0 60.0 40.0 0.0 16.7 50.0 33.3 25.0 41.7 3.3 ance (11) (1) (0) (6) (4) (0) (2) (6) <4) <3) <5) (4) Confor- 91.7 8.3 0.0 80.0 20.0 0.0 66.7 33.3 0.0 75.0 25.0 0.0 mation (11) (1) <0) (8) (2) (0) (8) <4) <0) <9) (3) (0) Fleshing 91.7 8.3 0.0 70.0 30.0 0.0 75.0 25.0 0.0 58.3 41.7 0.0 <11) (1) (0) (7) <3) (0) (9) <3) (0) (7) (5) (0) Finish 100.0 0.0 0.0 80.0 20.0 0.0 75.0 25.0 0.0 50.0 50.0 0.0 <12) (0) <0) (8) (2) (0) (9) (3) (0) (6) (6) (0) Blisters 100.0 0.00 0.0 100.0 0.0 0.0 100.0 0.0 0.0 100.0 0.0 0.0 (12) (0) (0) (10) (0) (0) (12) (0) <0) (12) (0) <0) 1 95.0 5.0 0.0 78.0 22.0 0.0 66.7 26.7 6.6 61.6 31.7 6.7 Tota (57) (3) (0) <39) <11) (0) (40) (16) (4) <37) <19) (4) Note: Figures in parentheses are base as for the adjacent percentages. 76 Table X. Percentages of broiler carcasses (five-week old) in each grade, by Protein levels and Rearing Protein levels 20% 22% 24% 26% Carcass quality Grade Grade Grade Grade Ectorg A B c A B c A B c A s C Cage (%) (%) (%) (%) Appear- 9.0 54.6.36.4 4157 58.3 0.0 8.3 83.4 8.3 50.0 50.0 0.0 ance (1) (6) (4) (5) (7) (0) (1) (10) (1) (5) (5) (0) Confor- 45.5 54.5 0.0 50.0 50.0 0.0 16.7 83.3 0.0 20.0 80.0 0.0 mation (5) (6) (0) (6) (6) (0) (2) (10) (0) (2) (8) (0) Fleshing 54.5 45.5 0.0 50.0 50.0 0.0 41.7 58.3 0.0 30.0 70.0 0.0 (6) (5) (0) (6) (6) <0) (5) (7) (0) (3) <7) (0) Finish 54.5 45.5 0.0 33.3 66.7 0.0 41.7 58.3 0.0 40.0 60.0 0.0 (6) <5) (0) (4) (8) (0) (5) (7) (0) (4) (6) (0) Blisters 54.5 45.5 0.0 83.3 16.7 0.0 58.3 41.7 0.0 80.0 20.0 0.0 (6) (5) (0) (10) (2) (0) (7) (5) (0) (8) (2) (0) T t 1. 43.6 49.1 '733 51.7 48.3 0.0 33.3 65.0 1.7 44.0 56.0 0.0 0 a <24) <27) <4) <31) <29) <0) <20) <39) <1) <22) <28) <0) Floor (%) (%) (%) , (%) Appear- 75.0 25.0 0.0 18.2 63.6 18.2 54.6 36.4 9.0 80.0 20.0 0.0 ance (6) (2) (0) (2) (7) (2) (6) (4) (1) (8) (2) (0) Confor- 75.0 125.0 0.0 81.8 18.2 0.0 90.9 9.1 0.0 lMLO 0.0 0.0 rmation. (6) (2) (0) (9) (2) (0) (10) (l) (0) (10) (0) (0) Fleshing 75.0 25.0 0.0 72.7 27.3 0.0 90.9 9.1 0.0 100.0 0.0 0.0 (6) (2) (0) (8) (3) (0) (10) (1) (0) (10) (0) (0) Finish 87.5 12.5 0.0 72.7 27.3 0.0 72.7 27.3 0.0 100.0 0.0 0.0 <7) <1) <0) <8) <3) <0) (8) <3) <0) <10) <0) <0) Blisters 87.5 12.5 0.0 100.0 0.0 0.0 100.0 0.0 0.0 100.,0 0.0 0.0 <7) <1) <0) <11) <0) <0) <11). <0) <0) <10) (0) (0) T 1 80.0 20.0 0.0 69.1 27.3 3.6 81.8 16.4 1.8 96.0 4.0 0.0 Ota <32) (8) <0) <38) <15) <2) <45) <9) <1) <48) (2) <0) Note: Figures in parentheses are base us for the adjacent percentages. 77 Table XI. Percentages of broiler carcasses (six-week old) in each grade, by Protein levels and Rearing Protein levels 20% 22% 24% 26% Carcass quality Grade Grade Grade Grade factors A B C A B C A B C A B c Cage (%) (%) (%) (%) Appear- 46.7 46.7 6.6 25.0 66.7 8.3 38.5 53.9 7.6 100.0 0.0 0.0 ance (7) (7) (1) (3) (8) (1) (5) (7) (1) (2) (0) (0) Confor- 13.3 86.7 0.0 41.7 58.3 0.0 30.8 61.5 7.7 100.0 0.0 0.0 nation (2) (13) (0) (5) (7) (0) (4) (8) (1) (2) (0) (0) Fleshing 46.7 53.3 0.0 41.7 58.3 0.0 46.2 53.8 0.0 50.0 50.0 0.0 (7) (8) (0) (5) (7) (0) (6) (7) (0) (1) (l) (0) Finish 66.7 33.3 0.0 50.0 50.0 0.0 69.2 30.8 0.0 100.0 0.0 0.0 (10) (5) (0) (6) (6) (0) (9) (4) (0) (2) (0) (0) Blisters 6.7 93.3 0.0 33.3 66.7 0.0 38.5 61.5 0.0 100.0 0.0 0.0 (1) (14) (0) (4) (8) (0) (5) (8) (0) <2) (0) (0) T t: 1 36.0 62.7 1.3 38.3 60.0 1.7 44.6 52.3 3.1 90.0 10.0 0.0 O a <27) <47) <1) <23) <36) <1) <29) <34) <2) <9) <1) <0) Floor (%) (%) (%) (%) Appear- 40.0 60.0 0.0 43.8 50.0 6.2 40.0 46.7 13.3 30.8 46.2 23.0 ance (6) (9) (0) (7) (8) (1) (6) (7) (2) (4) (6) (3) Confor- 93.3 6.7 0.0 87.5 12.5 0.0 93.3 6.7 0.0 76.9 23.1 0.0 mation (14) (l) (0) (14) (2) (0) (14) (1) (0) (10) (3) (0) Fleshing 86.7 13.3 0.0 87.5 12.5 0,0 73.3 26.7 0.0 76.9 23.1 0.0 (13) (2) (0) (14) (2) (0) (11) (4) (0) (10) (3) (0) Finish 80.0 20.0 0.0 93.8 6.2 0.0 66.7 33.3 0.0 69.2 30.8 0.0 (12) (3) (0) (15) (1) (0) (10) (5) (0) (9) (4) (0) Blisters 100.0 0.0 0.0 100.0 0.0 0.0 100.0 0.0 0.0 100.0 0.0 0.0 (15) (0) (0) (16) (0) (0) (15) (0) (0) (13) (0) (0) 1 80.0 20.0 0.0 82.5 16.2 1.3 74.7 22.7 2.6 70.8 24.6 4.6 TOta <60) <15) <0) <66) <13) <1) <56) <17) <2) <46) <16) (3) Note: Figures in parentheses are base as for the adjacent percentages. 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