MN | { MW ! I W ' N — _! I. — 1 1 M NH \ 3&5. W SOME FACTORS AFFECT'NG SPE§WATOGEN§515 AND FQRTMTY. Oi" GARY BULLS W193i: {at 1% Dawn 9% M. S. f fiC’éflGAN WAR CQLflM fiafixwfi' Chm“ 1mm $48 THESIS ’ I This is to certify that the thesis entitled ”Some Factors Affecting Spemetogeneeia and Fertility of Dairy Bulls" presented by Robert C. Lewis has been accepted towards fulfillment of the requirements for a . __M._S._degree in_Da.Lr¥___ ( f. flog/M Major 9(yéssor Baum m 1102038 MUG WOMSIS AND mTILITI GI DAIRY BULLS sot: norms memo moomsts m MIL!!! or mm ms ‘0! Robert Charlee Levie W A M818 Sublitted to the Gredute School of inchigen State college of Agriculture Inc). Applied. Science in pertlel fulfillment of the require-eats for the degree of mm 01‘ some: Deyutment of Dairy 19118 1‘ its '0 ‘t C. e LOUOWB i'he euthor vishes to express his sincere epprecieticn to Dr. I. P. Reineke, Professor of Physiology and Phemcolog. for lhis suggestions regarding the planning of this investigetion Ind to Dr. 0. I. when. lesserch Professor in mining, for his crit ice]. reeding of the nemscript. 'ihe writer is especially grateful to Ir. A. 0. heltser, k- tension Dairy-en end Secretery of the Ilichigen Artificial Dresders' Association for his cooperation in making the essocietion‘s records eveileble for analysis. !he aid of lies Mary I. has. of the Nettmetics Depart-eat. in preparing the statistical mlysis of the data presented is else gratefully echnovledged. 20330& IABII GI CONTEIIS IIIIODUOIIOE................................................... 31?!!! or LIEIRAIURI ...... . ........... ‘ ............ . ............ Selen.Gherecteristics..... ....... . ....... ....... ...... ..... Seasonal Viriation.......... ...... ......... ............... . lndocrine Relationship to fertilitr.... ............ L....... Endocrine Interactions................... ........ ...... Effect of the thyroid Gland.... ....... . .......... ...... lffect of the Anterior Pituitary Gland........ ...... ... Other rectors Affecting Zl'ertility. . . ...................... . lffect of Age............. ............. ..... ........... lffect of lzercise........................... ......... . Effect of fine of lreeding............................. lffect of Ascorbic Acid. ...... . ...................... .. Effect of Eyeluronidese.... ............ . ........ ....... Burner: of Review of Ldtereture... ........... . ............ . OBJEO!..... ......... . ......................................... . Source of Dete................................ ...... ....... scape of the Study......... ...... ............. ............ . “snags-eat of the Bulls.. ........... . .......... . .......... . .Hethod of Semen Ehndling................................... rabu‘tion Of Dat‘OOOOOOOOOOO00.0.0.0...0.. ..... O 000000000 . OUUHg 1 11 ...: 882%? RQRRR ”SMSOOOOOOOOO00.0.00........IOOOOOOOOOOOO.....OOOOOOOOOOOOO Yolane.................................................... Concentration...... ........ . ........ ..... ..... ............ rotel apernatosoe... .......... . .......... ..... ........... . Initial lotility...................... ...... ... ......... .. Individual and Honthly Variation.......................... Gorreletion between Senen 0herecteristics................. Effect of Light end lenpereture upon apernntogenesis...... Reletion of lenen Qnelity to Isrtility.................... Virieticn in Ibrtility;................................... Percent of Collections Shipped.. ....... . ........ .......... Collection Inilnres....................................... Libido........................................... ..... .... Breeding Besults.................................... ..... . Effect of Light and fenperntnre on Breeding Results....... DISCUSSImOOOOOOOOOOOOOOOO......OOOOOOOOOOOOOOOO0.00.00.00.00. WIOOOOOOCOOOOOO......OOOOOOOOOOOOO......OOOO0.0. ........ O BIBLIwWOOOOOOOOOOOOOOOOOO.....OOOOOOOIOOOOOOOIOOOOOOOOOOO P880 88 37 37 37 39 #2 ft 1.9 52 53 SOME FACTORS AIFECTING SPERMATOGENESIS AND FERTILITY OF DAIRY BULLS INTRODUCTION the develoPment of artificial breeding associations has directed in- creased attention toward factors affecting dairy bull fertility. The exten- sive use of older bulls with creditable breeding records has increased the average service age and.made it imperative that management practices be Va~ evolved which.will prolong the useful life of desirable sires. Before one can successfully promulgate recommendations for maintain- ing high fertility standards. there must be a clear understanding of the factors affecting fertility. Furthermore, accurate critera for measuring fertility must be developed. Although number of services per conception is the most useful measure , of fertility at present, it has the disadvantage of requiring considerable time for record accumulation. Various investigators, therefore, have cor- related semen characteristics with breeding results and semen quality is routinely used for determining probable fertility in artificial insemination work. Results reported from the various laboratories have differed somewhat, however. and it is evident that some of the semen characteristics have little correlation with actual fertility of the bull. Seasonal variation in semen quality and bull fertility have also been reportedwaltheugh the literature is not entirely in agreement. There are also some differences of opinion as to the causes of these variations. This study was undertaken in an effort to determine the correlation w/ -2... between semen characteristics routinely examined and fertility of bulls used commercially fer artificial insemination. It was also thought worth while to investigate some of the climatic factors which.may affect dairy bull fer- tility under Hichigan conditions. REVIEW OF LITERATURE Reproductive processes of domestic animals are complex functions undoubtedly affected by many interrelated forces. To entirely separate and discuss them one by one is impossible. However, in this thesis an effort has been made to separate these factors in so far as is practicable. Anderson (4) has reviewed much of the available literature concerning artificial insemination of’all classes of livestock.. §emen Characterigtigl. The need for rapid measures of semen quality highly correlated with fertility is self evident. Many workers have studied this problem with varya ing results. Anderson (2) early observed that the Iglumeof semen collected from sterile bulls is less than that obtained from bulls of high fertility. The concentration and initial motility of spermatozoa was lower in semen from the sterile bulls. Observations of the percent of abnormal spermatozoa show that sterile bulls averaged 17.6 percent abnormals while fertile bulls averaged 8.1 percent. Conflicting results were obtained by Dougherty and Ewalt (28) who were unable, with limited data, to establish any correlation between motility, per- cent of abnormal spermatozoa, concentration and actual fertility as determined by breeding results. Swanson and Herman (79) substantiated and furthered the work of Daugherty and Ewalt. The Missouri workers were also unable to cor- relate concentration, initial motility; percent of abnormal spermatozoa, volume. or pH with fertility. The preperty most nearly correlated with fer- L/e» tility was the length of spermatozoa survival with vigorous motility when the -14.... semen was stored at 100° 1'. When separate ejaculates from the same bull were considered. initial motility was roughly correlated with viability in storage. These workers found, as had Donham and associates (27) ten years before, that separate ejaculates from the same bull may vary considerably in their a» characteristics. Lesley and Bogart (41) obtained somewhat different results in a study of Hissouri range bulls used for artificial breeding. In this study volume. concentration and total spermatozoa per ejaculate were positively correlated with fertility. Resistance of the spermatozoa when stored in egg yolk buffer was also correlated with fertility. These workers agreed. however, that initial motility and percent of abnormal spermatozoa were not significantly correlated with breeding results. They further observed that the percent of spermatozoa surviving a cold shock in non-diluted semen is not correlated with fertility. A later study by Lasley (’42) indicated that semen rated at 1+0 percent motility is not as fertile as semen rated 61 — 70 percent motility. Considerable variation was found between semen samples taken from the same bull and between bulls in this trial. One of the important factors cans- ’a' ing semen variation was the frequency of collection. Semen volume, number of spermatozoa per ejaculate. percentage of abnormal spermatozoa and fertility of the bull increased as the interval between collections lengthened. Swanson and Herman (80) in 19% repeated their earlier study with similar results except for finding a significant curvilinear relationship be- tween motility and concept ion rate. Although semen with a low motility rating was of lowered fertility. that containing #5 percent or more motile spermatozoa gave nearly as high concept ion rates as semen with a higher motility rating-.0 Mercier (46) and Mercier and Salisbury (47) obtained positive correla- - 5 - tions between concentration and fertility and negative correlations between methylene blue reduction time, percent of abnormal spermatozoa and fertility. lot only were there significant differences between the semen characteristics of first and second ejaculates of the same bull and between bulls’but a strong breed difference in fertility was observed. The study involved bulls of the Holstein and Guernsey breeds. The Holstein sires were superior in many of the semen characteristics examined and were of higher fertility as determined by breeding records. That the semen from sterile bulls is characteristically alkaline has been shown by Anderson (3) and confirmed by Reps and Cannon (60). The in- creased alkalinity of sterile bull semen is associated.with lowered volume, concentration and decreased motility according to Anderson. He also states that the second ejaculate is normally more acid than the first and is higher in spermatozoa concentration and motility. Rape and Cannon have also pre- sented evidence indicating loggred fertility at high pH. As would be exp pected, the pH varied between bulls but tended to remain constant in the same bull. Reid and coworkers (62) have recently conducted an extensive investiga- tion into the correlation of the drOp in.pH of incubated semen to other semen characteristics. Highly significant correlations were found between the drop in.pH and concentration, initial motility, viability, and percent of morpho- logically abnormal spermatozoa. Laing (39) suggested that, although fertility appears to be impaired at low levels of semen quality, other factors Operate to vary breeding re- sults when semen of high quality is used. Mercier and Salisbury had the same opinion regarding Holstein and Guernsey fertility differences. The latter workers state their belief that the breed differences found are more than -6... would be expected from the differences in semen characteristics alone. Table I summarizes the correlations between semen characteristics and fertility as reported in the literature reviewed. It is obvious that, although there is agreement on the relationship of some semen characteristics to fertility, the situation is not clear regarding the correlation between all semen qualities and breeding results. Apparently other factors Operate to influence the results of studies of this kind. Addi- tional investigations are necessary if uniform methods of semen examination which will consistently indicate its fertility are to be deve10ped. gascnal Variation Livestock breeders have long been aware that some classes of farm live- stock are seasonal breeders. Although they may not Abe, completely sterile during periods outside the mating season, theirflfertility isimuchimpaired. Parker and McSpadden (53) have found seasonal differences in semen quality and fertility of Rhode Island Red males. The volume and density of the semen and the total number of spermatozoa were at peak levels during April and Hay. Fertility levels were higher from December to May than from June to lovember. A survey of conception records of milk goats in Great Britain has been made by Asdell (6). Conception rates gradually increased from August to October and then declined to a minimum during May. Very few conceptions occurred during the late spring and early summer months. Turner (87) made a similar study of milking goats in the United States. The results of this survey are very similar to those obtained by Asdell who found that in favorable seasons, does may breed in August, regular estrus cycles occurring from September to February or March and an anestrus period n : Raps 2 1 3 #133“ 3 .1211. Swanson : Lasley : Swanson : Mercier : Anderso y : 3 3 l9u0 : Anderson : Doughert 3 3 SEMEN CHARACTERISTICS CORRELATED WITH TERTILITY TABLE I. O. 0. Volume 0. Concentration Initial Motility O. O. 0. Total Sperm 0. Percent Abnormals 0. pH 0. O. O. 0. Survival Time 0. Resistance to cold shock 00 O. K B R T Legend = 0 Hot correlated with fertility e_:gorre ated with fertility from April through July. Shropshire rams underwent three periods of spermatogenic activity according to McKenzie and Berliner (1+5). Fertility was high from October to January, medium during the spring and very low in the summer months. Hampshire rams were of high fertility from August to January and were not as severely depressed in semen quality during the summer as the Shrapshire rams. Green (33) found the quality of ram semen decreases slightly but constantly from January to May. During June and July numbers of abnormal forms increased markedly. Density decreased from May to August. Semen quality improved during the fall reaching a peak in December. Rem semen studied by Phillips and coworkers (56) showed significant seasonal differences in motility, number of spermatozoa per cc., total spermatozoa, and abnormal forms. Semen volume did not vary significantly. Karakul sheep bred during the fall with few conceptions occurring from late winter to early summer according to another study by Phillips and associates (5?). A number of workers have studied seasonal variation in semen quality and fertility of bulls. nine:- and Graves (50) observed that the Beltsville herd required more services per conception in July, August and September than during the rest of the year. Il'he late winter and early spring months were periods of high fertility in Dawson's report (25). Morgan and Davis ( 51) found fertility to be highest from October to January and low in February, March, August and September under Nebraska conditions. Sires used for arti- ficial insemination in New Jersey were of lowest fertility in II'ebruary end -9- and “arch according to Weatherby and associates (90). Breeding records of the Purdue Universitygherd were examined by lrb and coworkers (30): Hay, with an average of 7%.} percent. was the month of‘highest efficiency and August, with 53.2.percent. had the lowest breeding efficiency. Seath and Staples (7”) determined that Louisiana dairy herds required more services per conception in the summer than during the other seasons. In a later study'of Louisiana dairy herds. Seath and associates (75) found breeding efficiency to be highest in the fall and winter and lowest during the spring and summer. llliott, Salisbury and Brownell (29) presented evidence which con- flicted with the previous studies on seasonal variation in bull fertility; These workers found fertility of bulls used for artificial insemination in low York State to be low in midwinter and spring but high in.August and September. Hilder and associates (36) also retina lebruary and March to be months of low fertility but disagreed.with Elliott and coworkers in finding July, August and September to be months of lowest fertility. Hercier and Salisbury (#8) (#9) have recently made an extensive analysis of seansonal variation in fertility of bulls used in new York State and Eastern Canada. The percent of successful services was significantly lower in winter and spring and higher during the slimmer and fall. An analysis of 51,587 breeding months in the Cornell University herd by Clapp (2“) showed an average of 2.11 services per conception. There appeared to be a trend toward greater efficiency from March.through July. breeding efficiency drapped sharply in.August and continued at a low level through Iebruary; July required 1.90 services per conception and Ibbrusmy 2.29 services per conception. Semen quality eminatione by lrb mid associates (31) showed it to be of superior~ winsulity. in the spring and low in qualitywdnring the ppm-er. he average semen 39.1953-“ initial notility was IleafielFJT‘J-io August and Septuber. The length of spermmsurvival was least inAugust and lower in July, September and lovember than during the other months. July, August and September were also months of high percentages of abnormal spermatosoa. Spermatosoa concentration and total spermatosoa per eJaculate were at high levels faring April, Hay and June. Observations were made by Phillips and coworkers (55) on volume, motility, number of spermatosoa per cc., total abnormal spermatosoa and proportions of abnormal hoads. necks, middle pieces and tails of semen collected from beef and milking florthorn bulls. Significant or highly significant seasonal differences were found in concentration, total yarn, and proportions of abnormal heads, necks, middle pieces and tails. Of 1,135 matings. 59.6 percent resulted infertile matings in April and no.8 percent in August. Swanson and Herman (81) studied monthly variations in initial motility, volume, concentration, livability in storage, pH and morphology of semen from bulls used in the University of lissouri aniry herd. he p3 of the semen was significantly lower inthe summer than in the fall. Initial mobility and viability in storage were lowest in the winter. Salisbury (71) found a highly significant decrease in the percentage of motile spermatosoa daring early spring and highly significant differences be- tween months in total spermatozoa per ejaculate. The lowest spermatozoa count was in August. there were, howaver, no significant fertility differences from month to month. -11- Significant individual and.monthly differences in density, motility, p3 and percent of successful collection attempts‘have been indicated by Anderson (5). He also noted marked seasonal variation in semen quality but cautions that there is considerable variation between bulls, farms and years. Teble II shows the seasonal variation in fertility found by the authors reviewed in the foregoing and Table III presents a summary of the seasonal effects upon semen quality. gadocrine Relationship to Fertility The well established fact that there is a seasonal effect on semen quality and fertility of domestic animals suggests that climatic factors such as light and temperature may be responsible. If such is the case, a logical mode of action is through disturbances of the endocrine system which is known to control development and functioning of the primary and secondary sex organs. Indocrine Interactions Knowledge of the interactions of the hormones affecting sexual activity is meager. Some facts, however, have been well established. “Thatthe anterior pituitary gland must be present for reproduction to take place is accepted. It is known that the anterior pituitary gland secretes gonadotropic hormones which control the development and action of the gonads. The thyroid gland also exerts an effect upon the gonads through its effect on cell metabolism. The thyroid gland also adds in regulating the rate of secretignof the anterior pituitary hormones. The anterior‘pituitary gland secretes a thyrotrOpic hormone which aids in controlling the amount of thyroxin TABLE II. SEASONAL VARIATION IN FERTILITY Althor 8 jpecies 8 High fertility : Low Fertility 8 8 8 Parker 8 l‘owl 8 Spring 8 Fall 8 8 : ‘ Asdell 8 Goat 8 Fall 8 Late spring 8 8 8 Early summer 8 8 8 Turner 8 Goat 8 Fall 8 Spring-summer ' 8 8 8 McKenzie 8 Ham 8 Fall 8 Summer 8 8 8 Green 8 Ram 8 Late fall 8 summer 8 8 8 Phillips 8 Karelml sheep 8 Fall 8 Late winter to 8 8 8 early summer 8 8 8 Miller 8 Bull : 8 Summer 8 : 8 Dawson 8 Bull 8 Late winter 8 8 : Early spring 8 Morgan 8 Bull 8 Fall 8 Early spring 8 8 Early winter 8 Summer 8 8 8 Veatherby 8 Bull 8 8 Late winter 8 8 8 Erb 8 Bull 8 May 8 August 8 8 8 Seath 8 Bull 8 Fall-winter 8 Spring-summer 8 8 8 Phillips 8 Bull 8 April 8 August 8 8 8 Elliott 8 Bull 8 Late summer 8 Mid-winter 8 8 8 Spring 8 8 8 Hilder 8 Bull 8 8 Late winter 8 8 8 Summer 8 8 8 Clapp 8 Bull 8 Spring 8 Late summer 8 8 8 Fall 8 8 8 Mercier 8 Bull 8 Summer-fall 8 Winter-spring SEMEN CHARACTERISTICS AFFECTED BY SEASON TABLE III. O. 8 Erb 8 Parker 8 Green 8 Philli lisbury 8 Anderson Bull Fowl .0 Volume 0. 0. Concentration Q. Total Sperm O. 13 - Motility O. a... O. 0. Percent Abnormals Survival Time pH Affected by season + -14... secreted by the thyroid gland.and gonadotropic hormones whichiregulate the activity of the gonads. The gonads secrete hormones which depress the rate of secretion of gonadotrOpic hormones from the anterior pituitary. It is logical to expect, therefore. that any factor whichd'fects any one of these glands may exert a secondary effect on any of the others. Effect of the Thyroid gland An extensive review of the physiology of thyroactive substances has been published by Reineke (65). The exact mechanism by which thyroid functioning affects spermatogenesis and fertility is still a matter of conjecture. The deve10pment of a relatively inexpensive synthetic compound having thyroidal activity by Reineke and Turner (6“) (88) and realization of the value of thiouracil as a goitrogenic substance (9) has stimulated research into the thyroidal relationship to fertility of domestic animals. Smelser (76) tested the effect of thyroidectomy of male rats on the gonadotropic activity of the anterior pituitary gland. No effect upon the amount of gonadotrOpic hormone in the anterior pituitary was found although the authors suggested that the release of the hormone into the blood stream is re- duced. A definite depression of testicular function was observed and sperm production was decreased. The weight and morphology of the testes was not affected although reduced weights of the accessory glands indicated a reduction in testis hormone secretion. That the relationship between thyroidectomy and gonadotroPic activity of the anterior pituitary gland is not clear is indicated by the fact that Reineke and associates (63) found decreased testes size and - 15 - decreased gonadotropic hormone in the anterior pituitary of thyroidectomized goats. Beineke and Turner (64) pointed out that after domestic animals have completed their growth the secretion of the thyroid gland gradually decreases lowering body metabolism and the animals begin to fatten; sluggishness, de- creased sex drive and lowered fertility of bulls and irregular estrus cycles of cows are often found. Administration of thyroactive material will aid in returning these hypothyroid animals to normal sexual activity. Many species of animals undergo a period of anestrus during the summer months. Thyroxine or therprotein administration has been found to inhibit this summer sterility. Thiouracil administration or thyroidectomy has caused spermatogenic effects similar to those normally found in summer sterility. These observations have indicated an effect of temperature upon the action of the thyroid gland and Dempsey and Astwood (26) have shown.that the thyroid secretes less hormone when the temperatures areliigh. Wells and Zealesky (91) changed ground squirrels from seasonal to con- tinuous breeders by subjecting them to a low environmental temperature. Jean 0?) fed daily doses of 0.25 to 1.0 gm. of dessicated thyroid to Mallard drakes whose testes normally increase in size during late winter and early spring. The testis size of those drakes receiving the thyroid prepara- tion ranged from two to ten times the size of the controls. Increased spermatogenesis in preportion to the increase in testis size was also observed. The largest testes contained large numbers of fully formed spermatozoa while the smaller testes showed only division figures. Testis growth of ducks, which is stimulated by light, is inhibited for - 16 - a short time by thyroidectomy according to Benoit (12). Since the effect gradually decreases, it is probable that the thyroid is only one of the factors involved. Blivaiss and Domm (16) observed that Brown Leghorn cockerels thyroidec- tomized when u to 20 days old exhibited only early stages of spermatogenesis by the time they were 8 months old. When White Leghorn cockerels were fed 100 mg. of dessicated thyroid three times weekly, the usual seasonal decline in semen volume which occurs during May, was increased according to Titus and Burrows (85). When the treat- ment was discontinued semen volume temporarily increased indicating the dosage level was probably too high. Greenwood and Chu (34) found that feeding 20 mg. of dessicated thyroid to a Brown Leghorn male completely prevented the regression in testis size and cessation of spermatogenesis observed in thyrodectomized controls. Martinez-Campos (#4) found that when o.ou percent of thyr0protein.was added to the ration of poultry marked increases in semen volume and total spermatozoa occur. Spermatozoa concentration also increases but to a lesser degree. At 0.01 percent and 0.02 percent levels the therprotein caused only slight increases in spermatogenesis. Thgedata hanbeen confirmed by Hilwerth (93) who also obtained marked increases at the 0.04 percent level. When fed as 0.08 percent of the ration thyroprotein greatly depressed the semen volume, concentration and total spermatozoa. These data would indicate therefore that the Optimum level is approximately 0.04 percent of the ration for male fowl. Gunn (35) found that seminal degeneration and low fertility of rams was associated with temperature. Berliner and Warbritton (13) have shown that - 17 - temperature fluctuations affect the thyroid and, through it, the gonads of sheep. Bogart and Mayer (17) (18) concluded that a lack of thyroxine, inhibited by high summer temperatures, is a major cause of summer sterility in rams. Semen variations associated with summer sterility were decreased or prevented by feeding or injecting thyro-active materials providing the interstitial cells had.not previously become degenerated. In the fall, when rams are normally fertile, thiouracil administration produced changes similar to those observed during the summer. Thyroxine counteracted the effects of thiouracil. That the effect of heat is not always produced by . direct action on the testes is indicated by the fact that the temperatures causing relative sterility may be below the normal body temperature of the ram. ‘ _ Turner and coworkers (89) were able to improve the quality of semen from a.ram with good libido but low quality semen by feeding thyroprotein. They also increased the libido of a Toggenburg buck by feeding one gm. of thyroprotein daily. U “i I.,x Petersen and associates (5“) thyroidectomized a male Jersey calf and observed its sexual development. Although his testes development was apparently normal, there was a complete absence of libido. Semen samples \ obtained by massaging the ampulla were fertile.' Feeding 25 gm. of dessicated - thyroid over a period of three days restored normal sexual behavior. These findings led to the conclusion that although libido may be controlled by the thyroid gland, spermatogenesis is apparently unaffected. When a Jersey heifer was thyroidectomised she failed to exhibit any estrus cycles according to Brody and Frankenbach (21). Therprotein adminis- tration resulted in several observed estrus cycles. -18... Spielman and associates (78) also observed the lack of estrus in thyroidectomized cattle but reported that regular ovulation does occur. Artificial insemination as long as #53 days after thyroidectomy resulted in conception and the birth of normal offspring. In field trials, Reineke (66) improved vigor and libido in ten of fourteen bulls with poor breeding records through feeding 0.5 to 1.0 gm. of thyroProtein.per hundred pounds of body weight. Limited conception records indicated improved spermatogenesis. Knocp (38) fed eleven problem bulls a supplement of potassium iodide and.skim milk. Semen of all the bulls showed improvement in one or more of the following qualities: volume, total spermatozoa, percent of living spermatozoa and initial motility. Im- provement in libido was also evident. Schultze and Davis (73) fed 1.0 to 1.24 gm. of therprotein per hundred pounds body weight daily to seven bulls for thirty days. Initial motility of the group showed definite improvement. The percent of abnormal spermatozoa changed little except in one bull where it decreased markedly. This partic- ular bull formerly had a very high percentage of abnormal spermatozoa. Con- ception rates of five of the bulls increased from anflaverags of 51.7 percent to 55.7 percent within the first ten days. After ten days the conception rate increased to 58.6 percent and during the ten days after feeding stopped the conception rate further increased to 60.h percent. Seven other bulls used as controls exhibited no changes in breeding efficiency during this time. The low summer breeding efficiency found among Louisiana dairy bulls by Seath and Staples (7b) was attributed to the high temperatures found in that area. Clapp (2h) made a similar suggestion regarding the lowered efficiency of the Cornell University herd during the month of August. - 19 - Effect of the Anterior Pituitary Gland _ It has previously been indicated that it is probable that the effects of temperature and thyroid activity upon spermatogenesis are largely a matter of stimulation or inhibition of the activity of the anterior pitui- tary gland. There is evidence. however, that in some cases climatic fac- tors may act directly upon the anterior pituitary. Light has been found to stimulate spermatogenesis, presumably by acting directly upon the anterior pituitary gland.o Rowan (68) has reviewed the literature regarding the effects of light upon spermatogenesis in some fifty species of animals, birds and fish. He has suggpsted that the effect of light on birds may simply be one of keeping them awake and active. This activity in itself stimulates the anterior pituitary gland to produce inn creased amounts of the gonadotroPic hormones (6?). Bissonnette (1h) however, has presented rather convincing evidence that the effect of light is through the eye and along nerve channels to the pitui- tary. There are species differences in response to light stimuli. Some species increase in sexual activity as the days grow longer and others de- crease in.activity. The response in either case appears to be in direct pro- portion to the amount of stimulus. Iiske (32) demonstrated that the anterior pituitaries of female rats kept in the dark were low in follicle stimulating hormone and high in leutinizing hormone. As would be expected, the esture cycles were abnormal. The pituitaries, gonads and vesicles of male rats kept in the dark were smaller than those kept in the light. Through increasing periods of illumination from October 10 onward, Bissonnette and Csech (15) were able to change the breeding season of raccoons from Iebmry to Docember. When Southdown sheep were transported across the equator they changed their breeding season to correspond with the hours of daylight even though it meant two breeding seasons in one year according to»Harshall (#3). Ulson (52) has shown that exposure to direct sunlight is not necessary for normal reproduction of cattle. A decrease in the number of services per conception when cattle were exposed to unrestricted sunlight was found by Quinlan and Benz (59). Anderson (1) has presented evidence of a correlation between.periodicity and duration of estrum in cattle and hours of sunshine. Glapp (2h) attributed the varia- tions noted in breeding efficiency of the cornell University dairy herd to be largely due to changes in the length of day. Nercier and Salisbury (#8) (#9) here extensively studied.the effect of light upon breeding efficiency of dairy cattle kept under New York and eastern Canadian conditions. In both cases light and breeding efficiency were significantly correlated. Variable results here been obtained.when gonadotrOpie hormones were used to treat sterility in cattle. Bottomley and coworkers (19) were able to re- store fertility to three bulls and several cows through injecting'verying amounts of human pregnancy urine extract. Asdell and associates (7), however, were unable to note any results from administering gonadotropic hormones to sterile cows. The latter workers caution that the high rate of spontaneous recoveries often encountered render it difficult to give correct interpreta» tion to the findings. -21- Other Il'actors Affectipg J‘ertilitz Iffect of £53 A difference in breeding efficiency between young and old bulls was '1 found by Killer and Graves (50) Ana study of the Beltsville herd. Young I ~ bulls appeared to be 39.19 fertile than mature bulls when bred to fertile 60'! e - g p re. . / ' (Viz? Tanabe and Salisbury (81+) found cows increase in conception rate up tgwfour_years. Between__!1__Ve. and. seven years they remain at a high level ' of fertility and then gradually decline with advancing age. Young bulls, however, gave greater breeding efficiency than older bulls. he peak con- ception rate was for two ”331-2191. bulls although those from one to three years old were of higher fertility than those of other ages. An age difference in response to seasonal variation was observed by liercier and Baliis (#8). Young and old cattle appeared to be more readily influenced by climatic conditions than mature cattle. Bulls under six. years'of age did not respond to light variations as well as older bulls. The authors suggest these younger bulls may be more subject to other in- fluences than older bulls. Baker and meansberry (10) were unable to find any fertility differences between old and young range beef bulls. However, since the older bulls had been selected for big: fertility it is likely that any differences were ob- soured. Heifers required more services for their first conception than for later conceptions in a study by Bowling and associates (20). A higher fer- tility level among young bulls was apparent since the heifers required fewer services per conception when bred to then than.when mated to older bulls. Yhere was a gradual decrease in breeding efficiency of bulls as they grew older. this decrease was significant with six year old bulls. Studies among human females by Ashley (8) indicated that many of them are sterile for up to several years after puberty due to lack of ovulation. this same sterility of immature females has been claimed for the mouse, rat and cow. These findings may indicate one of the reasons for a lower con, ception rate among heifers bred for the first time. Effect of Exercise That preper exercise contributes to the physical well-being of the bull and increases spermatogenic activity has been indicated by some workers. , r- Bartlett and.Perryl2ll; found regular exercise of the bull increases the volume_of the semen§/:i;odward‘(9b5;dncreased motility and longevity 9f¥€he spefimatosoafbyzdaixyenercise. Service time was also decreased in the case gfwslow bulls. The lower quality of semen obtained during Iebruary'and March byfieatherby and associates (90) was believed to be due to lack of exercise during these months. ’ ,0 lffect of rm of Breeding <1. I? ; 5 / Yrimberger g g; has found the duration of estnmn'to range from 2.5 to 28 hours with an average of 16.9 hours. Ovulation occurs three to 18 hours, with an average of 10.5 hours after the end ofestrum. Breeding results indicated a trend toward higher conception rates if cows were bred six to 2h hours before ovulation. Conception rates were low among cows bred within 12 hours after ovulation. -23- These results indicate that cows first observed to be in heat in the morning should be bred that afternoon. and those in heat in the after- noon should be bred the following morning. The findings of Trimberger confirmed earlier data presented by Werner and coworkers (92) which showed that most cows ovulete by the end of the second half day following estrus. In this study 56 of 113 cows were in heat for only one-half day. Laing (40) has reported similar findings in England. Estrus varied in length from six hours in December to 30 hours in July. The yearly average was 16.1 hours which is very close to that reported by Trimberger (86). Except fer the‘dnter months Laing found hand breeding to be less efficient than free service of the cows. A Inggested explanation is that often. when breeding time is controlled, the cows are bred early in the heat period and the spermatozoa die before ovulation takes place. No preg- nancies resulted in this trial when cows were bred more than 16 hours before ovulation. Effect of Ascorbic;§cid Of 29 bulls which Phillips and coworkers (58) treated with ascorbic acid, improved fertility occurred in all but four. One of these rapidly improved when vitamin A.was administered. One bull which failed to respond to ascorbic acid treatment had atrOphied testicles. Eleven of the bulls were returned to active service after treatment although they were to have been discarded prior to administration of the ascorbic acid. Scheidenhelm (72) recently tested the effect of feeding chlorobutanol to problem bulls and cows. An increase in libido was evident and the number -24.. of services per conception was reduced. Young sires were more readily affected than older bulls. chlorobutanol administration also aided in settling some difficult cows. Reid and Sykes (61) presented evidence which indicated that ascorbic acid acts in the guinea pig by stimulating the production of gonadotropic hormones by the anterior pituitary gland. lffect of gyaluronidase Hyaluronidase has been shown to disperse the cumulus cells surround- ing an ovum in vitro but its role in actual fertilisation is uncertain. Swyer (82) found a close correlation between hyalurenidase content of the semen and numbers of spermatosoa in rabbits. bulls, boars, and men. lo correlation was evident in the case of dogs and fowl. i'he fact that semen from cryptorchids contains no hyalurenidase indicates that it is secreted by the seminiferous epithelium rather than by the accessory glands. In a later study Buyer (83) found at least three-quarters of the waluronidase in semen is associated with the spermatozoa. The spermatozoa appear to set as liberators rather than producers of the hyaluronidase. Recent studies by Chang (23) have led him to conclude that the seminal fluid rather thanhyaluronidase really increases the fertilising capacity of spermatosoa. Mg of Review of Literature Reports of the relationship of semen quality to bull fertility have varied (2) (28) (#1) (it?) (79) (80). Recent investigations (60) (62) indi- cate that initial semen pH or the fall in pH after incubation for one hour ? .'25- may be the best laboratory measure of semen fertility. Emmy semen characteristics have been shown to be influenced by climatic ehanges (5) (31) (55) (71) (81). met the seasonal variation in fertility is not uniform from one geographical location to another is evi- , dent (31) (#9) (75). Several workers (17) (26) (35) have demonstrated that fertility may be affected by temperature while others (15) (#8) (b9) (77) have shown an effect of light variation upon spermatogensis and fer- tility. ‘ Other factors such as age (8%), amount of exercise (11) and time of breeding (86) may affect breeding results. Improved fertility has resulted in some cases through ascorbic acid therapy (58). The hyaluronidase content of the semen.may also be a factor in determining male fertility (82) al— though its role in fertilisation is not known. OBJECT Ehe purpose of this investigation is to study the relationship between semen qualities routinely determined in an artificial breeding cosperative and actual fertility of the bulls involved and to investigate the effect of light and temperature upon germatogenesis and fertility under southern Iichigan conditions. mmnmw P30011113] guru of Data Records of the lichigan Artificial Breeders Association whose bull stud is located at East Lansing, Iichigan were the source of data for this study. e of tu Semen and breeding records of 24 fertile bulls of the Holstein and l? bulls of the Guernsey breeds used by the association between June 1, 1944 and April 30,19”? are included. More than 15.000 semen collections and over 107,000 breeding records are represented. Mat of the Bull! Until late in 1%5 bulls of the two breeds were housed together in a poorly lighted barn equipped with box stalls. Yhe Guernseys were then moved to another poorly lighted barn and were mnfined in stanchions. Both groups received the some ration which consisted of a 15 percent protein concentrate mix and average quality alfalfepbromegrass hay. the ration met all nutritional requirements so far as is known. -27.. lone of the bulls received adequate exercise. mring warm weather in 19144 and l9+5 they were tied out of doors arch of the time but the amount of exercise received was limited. Later the number of bulls became too great to be staked out. A mechanical bull exerciser was obtained but has not worked satisfactorily. Ming cold weather the bulls have been given even less exercise. It was planned that the bulls would be ejaculated into an artificial vagina. with a cow chronically in heat as a teaser, at weekly intervals. However. because of fluctuations in demand and other reasons. the intervals varied somewhat. Usually the variation was toward longer periods between collections. - In most cases the bulls were ejaculated twice with a short interval between the first and second collections. In a few cases third collections were made but these have been omitted from this study. flatbed of fiemen Handligg Semen collections were made on Honday, Iednesday and lriday mornings of each week. At first all of the bulls were ejaculated in a breeding shed attached to the laboratory of the association and the semen taken into the laboratory immediately after the collection was made. After the Guernsey bulls were moved to the second barn. whiohwas located about an eighth of a mile from the laboratory. they were ejaculated there. As soon as it was collected, the test tube containing the semen was placed in a thermos bottle containing water at 35-40° II'. and then taken to the laboratory by automobile. It normally was in the laboratory within five to ten minutes after the collection. In the laboratory, the semen volume was first recorded and a sample -28- taken for concentration determination in a photoelectric colorimeter, (Salisbury and coworkers (70) ), and motility rating under the microscope. the concentration is reported as thousands of spermatosoa per 3. and initial motility as percent of progressively motile spermatosoa. If the concentration and motility were adequate, the semen was diluted with buffered egg-yolk citrate prepared by the method of Salisbury ad associates (69) and placed in a room refrigerated to “0° l'. he diluted semen was then packaged in special containers containing. ice for parcel poet shipment to the inseminators. 'i'he semen was dispatched the same morning in which it was collected and received by the inseminatore that afternoon or the next morning. Thus the semen used was never more than three due old when the cows were bred. gab_1y._ation of Data Records of each attempted collection fromeach bull whether the semen was used or not was considered and monthly averages tabulated for the following: lumber of attempted collections. lumber of successful collections. lumber of collection failures. “time required for service. Semen volume per ejaculate. Bpermatcsca concentration per ejaculate. . 'rctal spermatozoa per ejaculate. . Percent initial motility. 9. lumber of cows bred. lo. lumber of cows returning for service within 30 to 60 days after breeding. 11. Percent of cows not returning within 30 to 60 days after service. caucus-Rump The monthly averages were then combined with the some months over the thirty—five month period covered by this study. The monthly data. therefore, - 29 - 3:: presented in twelve monthly periods. Seasonal data were obtained by combining the monthly data into four seasons composed as follows: 'intgr firing me; Fall December March June September Jamary April July October I‘ebruary May August lovemb er In the calculations to determine the percent of cows not returning for service within 30 to 60 days after insemination the number of cows bred and the number of cows returning for service were totaled for each cf the twelve monthly periods and the percent of non-returns determined. seasonal variation in percent of non-returns was calculated in a like manner. In the determination of the relationship between semen characteristics and fertility only that semen shipped to the inseminaters was considered. RESULTS fables IV and Y and Il'igures 1 through it summarise the monthly and seasonal data on semen quality obtained in this study. Yolu_a_g With the exception of the months of June and July the Guernsey bulls excelled the Holsteins in semen volume. This was the only semen character- istic in which the Guernseys were superior to the Holsteins. The Guernsey bulls produced a greater volume of semen per ejaculate during each of the four seasons than the Holstein bulls. Both groups of bulls gave a greater volume of semen per ejaculate (hiring the spring months than at other times firing the year. Ian was the season of least volume for the Holsteins while the Guernsey bulls were at equally low levels during the manner and fall . Concentration Semen from the Holstein bulls was consistently of higher spermatosca concentration than that from the Guernsey bulls. Considerable monthly variation in concentration was found. The season ofhighest concentration was found to be the mar while the lowest concentration was found during the winter for both breeds. fetal finermatosoa As would be expected from the greater semen volume of the Guernsey bulls and higher concentration of germatosoa from the Holstein bulls. the total number of spermatosca per ejaculate did not differ greatly between the two breeds. An examination of the monthly averages shows the Eolsteins were in -31- MONTHLY VARIAIION IE SEMI! QDLLITY 2A!!! IV. : Initial Total ...m .10 16 .....r «a M I... a O an an. a1 "1.. .1. GB :0. n O 1 e .we mo 00 n o G 0 mm 0 Y h t n o H G H 3 file 8 6 A‘s afe 0e [be 3 1 5 J e e 5 5 5 5 [Os 5 6 5 5 5 5 5 se so we so ee ee ee ee ee we 00 ee ee ee ee ee ee ee ee we ee “$flflflflfinwnw 008......:z‘88‘::00::‘::::::::300 55 9 Wflflflfl77n~mné emammcnxewu 5 76766 eeeeeeeOOOeOeeOOOeeOOe: nv nu 1i no my n“ 1i m“ al 7 6 m 00...... m. n ..‘8:::..:::'::::::::::OQ:O.::: 111 1.11 :‘8..:....:: 51.46 36 51.. ans <1 ,m ,o ,o ,o .3 :1 no (J <4 0.880.000.0000;.3:::‘:::::::: n. L ..e lovember an n :1: 0.3::00‘::..::::800::: December 4.6.; ...er -32- msomu. vmnrxou In sum QUALITY IABLI V. 2 3 Initial : Motility Percent H : G 8 e Total m G . ..n mm e1: m1 e1 en. E n O i G mm no: “0 m .n c G W 1 .0 N n o . a «war. W n 0.0.8:..00000... n. e; er at .03 .33 W 2 7 en 6766 .~ 38:38:00.... 6.h9 7 31 7.36 6.”? :8:::..::.. 1045 llhl 1192 1101 1 0.00.... E O. m 0. O. -33.. C o - ‘ ‘ tap" ann.-.Lb, c , v.1 ‘_ O ['J t5 0' Fir. l. ._ .' 1.. '.' -1 i r}; U) \3 ‘-‘ - ’ l‘ a r p D n .I ..I 3 r) 1 j? ~ ‘ .. f‘) r '° «1 ' 1 ‘ ‘f ‘ Ml. Sfimen Per Ejaculfit e . .._. l I.” ‘ v L‘ t .1 x J W (‘ . v _; ‘ ." 'J .4 "J .. .1 \- 7‘ ‘3 .-.,\. ...J. .> I 303:. o. 5 .6 MU" 1‘ u ‘. . .I b. . 1 a «n u‘ L w a. I 4.J.4 v . nusdoxV O. . a .4 ob 4‘ . . I; . 4 fax. p 4 . 1 . . \ V141; 4.4- . . u w - 114,1 I. p y -' 5.0 T‘ “.7 :1“: L... o‘ , 1‘ ,1] M () .5 -35.. Monthly :1 C1 C4 >> (A <) 1: t1 * .. j ' ' c i .7) ( J ’3 IT) 9‘: ~ ’ .t f. i 'N‘ k ,- ._: I" m J- 1" \V\ ‘..- (- ,4 ..2 W1); : 1' VDZJQ ‘ Setsonaily m (.9 ‘3' {1' ; L) .~. .2 3 D L . ‘3 -36.. Le:end Holrt>in A ---«-' v11? ‘1“. 397 \) fipr 'Jnv m 0 2 U m m ‘9 ““3 D o o m +~ " i“ 9 3 (r < n 3 w J *” d . .. . . _ t , ..9 ;.i 'D r 71“" “(+n .1.) .‘u U u U -37- general slightly mperior to the Guernsey bulls. The total number of spermatozoa per ejaculate were at high and low levels during the spring and winter respectively for the Guernsey bulls. The Holstein sires produced slightly more spermatozoa per ejaculate dur- ing the sumer than during the spring. ll'all and Winter were seasons of lowest total spemtosoa counts for the Holstein bulls. Initig Hotilitz The Holstein bulls slightly exceeded the Guernseye in percent of progressively notile spermatosoc observed inediately after collection of the semen. the percentage of initial notility was at high and low levels during the spring and winter respectively for both breeds. Individual and floaty Variation Since observation of the data indicated a variation in seaen characteristics between bulls and between months, the analysis of variance according to the method of Snedecor (7?) was lads. Highly significant individual differences between hills of both breeds ‘% found in every senen characteristic measured. Variation in total spar-atosoa per ejaculate between months was highly significant in the Holstein senen. The Guernsey senen exhibited significant nonth1y variation in initial motility although the value was low. 3;: data ‘1'; summarised in Table VI. Qgrrelation Between gmen maracteristic; Correlation coefficients between the various semen characteristics were calculated in order to ascertain any possible interactions between then. -33- EARL] VI. SUMMARY OF ANALYSIS OF VARIANCE GP SEMER CHARACTERISTICS §gurce of Variation ”O. ”O. ...—Bella = “MILL H : G 1:. H : 0 z : z : Voluae : 8. 55": 7.02“ x 0 .9“ z 0.72 z x x : Concentration : 3.b3**: 3.27*‘ : 0.u8 : 0.82 z z : a Total onrn : 5.?1**: 5.98** z 3.13** z 1.05 : x 3 8 Initial Hotility 8 6.32“: 3.46** 8 1.51 : 1.91”I : z 8 8 ‘ Statistically significant at 5 percent level of probability *' Statistical si ificant at ercent level of robabilit EARL! VII. CORRILAIIOH BETWEEN SEMEN CHARACTERISTICS : : Total : Initial 2 Concentration : §pern : Hotilitz : :gf : G : jg : G x g, z 0 z x x z z 3 Volume 3 O t O z i : f z * : Concentration : -- : -- : f : f : 0 : z x z z : : fetal Spars : -- z -- : ... --- : * z i : : : : .0 .0 8 0 - lot statistically significant * - sun-noun significant at 51 level of probability 1 - §tatigtically significant at 1% level of'probahility no results are contained in Table VII. Highly significant correlations between volune and total spermatosoa per ejaculate and concentration and total spermatozoa were obtained for both breeds. Semen of the Holstein bulls also showed a significant corre- lation between volune and initial motility. ~‘Correlat ions between concen- tration and initial motility were higaly significant for the Guernseys. A signifth correlation between total spermatozoa and initial motility was obtained in the Holstein semen. The same correlation was higaly significant for the Guernsey bulls. lff t of ht d To erature o rmato no i In view of the seasonal variation in semen quality found in this study and reports of climatic effects upon spermatogenesis. correlations between ligt, temperature and semen characteristics were calculated. To allow for any delayed effect of these climatic factors upon spernatogenesis the corre- lations were determined for the current, first and second preceeding months and seasonally. The correlations between light and spermatogenesis are emerised in Table 7111 and the data for temperature effects in Table 1:. Iigure 5 shows the hours of daylight and degrees of temperature by month and . season for comparative purposes. The data on light and temperature ’zébeobtained from the United States Veather Bureau at last Lansing. An examination of tables VIII and II shows that light variation appears to have a greater effect upon spermatogenesis than does temperature. Both current light and current temperature appear to be more effective in influencing spermatogenesis than the light and temperature of previous months. mu VIII. CORRELATION BETWEEN LIGHT All? SPEMATOGENESIS : z z a : Current : One Month : the months 8 : Month : Previoug : Previous : gasong : H x G : H : G : H a 0 x H a G a x x : z : : 2 Volume : t x 0 z 0 : 0 z 0 : 0 z 0 : 0 z z : z z z x : Concentration : 0 z i z t z I: a 0 x * x * z t : z z : z x x : i'otalSpera :i:t:0:o:oxo:o:o : a : z z x z 3 Initial Hotility : l- : .1. : t 3 i x 0 z t : 0 : *- z x : x x z z : 0 - lot statistically significant " - Statistically significantpat 5 percent level of probability t - gtatigticallz significant at 1 percent level of probability can II. CORRELATION mm W ARD SPEMATOGIRESIS : x : : : Current 8 One Month .: Two Months 3 : honth : Previous : Previou! : gascnal : H z 0 z E : C x g 2 G : H : 0 z z a z a z x : Volume 2 0 z 0 x 0 x 0 z 0 : 0 3 0 z 0 : x s x x x z : Concentration : 0 x {I z 0 z ¢ 3 0 : 0 t 0 z 0 : x 8 x a z z 3 total Sperm : 0 x o a 0 z 0 : o : 0 x 0 z 0 z : x 8 z z 8 : Initial Motility : i : a! z o x * z o x o : o z o z x 8 t x 8 : : 0 - lot statistically significant * - Statistically significant at 5 percent level of probability - tati tical i ificant at are level of robabi it '1 ..nl- "' . ' ‘ . ‘ ;- ' . C4 “1 .-.. r — ‘ a ‘4 .17 (n O ‘5 t) J. ’ 1 (7 "i o . l O o - . J n J ‘ ,4 a! > bi ‘b o L) : ;-. 2,. l’ ,, *3 1 '--: .3 - {7 .i» <1 J ”.2‘ J, , w - - 'b *1 - 1" - "' .~~ ".1 w {v ,' C) '1 I '3 «I ~ C Y" “P ‘ o‘ n "‘ 2 '0‘“ “VI ‘ wfiafbl‘a ‘2“ '5,- ‘ A s ‘ I‘i { . -J a a u — - i.’ - ...;k V J \A"). - 5., ‘ —~- 4 - .. e -l&2- here are some indications in thtsedata that there may be a breed difference in response to light and temperature stimulation. lo significant seasonal effect of temperature was observed from these data. Light variation signif- icantly affected semen concentration of both breeds and the initial motility of the Guernsey semen. Since light and temperature are highly correlated it was believed that the data in fables VIII and I! might be confounded. Therefore, partial correlations were calculated between the so two variables and semen character- istics. Data fbr the second previous month.was omitted from these calculations because of the very slight effect it had shown in the previous data. he results of the partial correlations are summarised in tables 1 and II. ‘!he decrease in effect of both light and temperature when considered alone as compared to the results when they are considered together is doubtless due to the interaction of these two factors. Ieither one alone is as effective as the two combined. Elation of flan flit; to l'ertilitz fhe data on semen volume, concentration. total spermatozoa per ejaculate and initial motility of the semen shipped for breeding purposes was correlated with breeding results, based on the percent of 30-60 day non-returns after service. Statistical analysis showed none of these measures of semen qmlity to be significantly correlated with breeding results in the field. -ug- EARL! 1. MC! 01' LIGH‘ VIE TEMPIRATURI CONSTART : : z 3 Current 8 One Month : Seasonal : Month 8 Previoup : : H a G : H : G : H x G x z : : 3 : Volume : t z 0 z 0 a 0 : 0 z 0 x z z z : : Concentration 8 O : O : O 8 O : 0 z ¢ : x : 8 z x fotal Sperm : t z 0 8 0 z 0 8 e : 0 3 x : 8 8 3 Initial Motility : i a f : 0 x 0 z 0 z 0 z x 8 8 8 z 0 - lot statistically significant " - Statistically significant at 5 percent level of probability 1 - Statist icallz sigificant at 1 percent level of probability TABLE II. m 01‘ mum WITH LIE! CONSTAHT z 0 — lot statistically significant " - Statistically significant at 5 percent level of probability t - fiatisticalg sigpificent at 1 percent level of probability 3 z : : Current : One Month : Seasonal 8W : z n : G : j: x G s 4 z : z 8 x 2 : Volume : * : 0 z 1' z 0 : 0 3 0 z : g : a : Concentration : O z 0 : 0 x 0 8 0 : 0 : t 8 8 8 a Total Sperm : 0 z 0 : 0 z 0 z 0 : 0 3 3 3 3 3 3 Initial Hotility : 0 z I- : 0 : It : 0 : 0 z x : z s Variation in l'ertilitz Data regarding the number of collections attempted. shipped. and un- successful attempts with the percentage of each are shown by month and season in ‘i'ables III and XIII. l‘igures 6 and 7 present graphically the monthly and seasonal variations in percent of collect ions shipped and per- cent of collection failures, respectively. Percent of Collections Shipped i‘he month of May with 93 percent of all collections attespted being shipped was the peak month. A lower percentage of the semen was shipped during lovember, December and January than at other times of the year. Spring and summer seem to be seasons of Optimum semen production. Collection l'ailurep i'he percent of unsuccessful collection attempts was higher for the Guernsey bulls than for the Holsteins. The percentage of collect ion failures for both breeds were at lowest level during the fall months. The highest percent of failures in the Guernsey breed occurred in the winter while the Holsteins had aslightly higher number during the spring than in the winter. gibido An estimate of the time required for each collection was made by the collectors and has been used as a rough measure of libido. Figure 8 gives a graphical summary of the data. lo great breed difference was observed although some individual variation was evident. In general. libido when measured in this manner appeared to be at lowest levels (hiring the hot summer months and highest during the winter. EARL] XII. COLEBCTIOH DATA.SUHMARIZED BY'MONTHS -1185- lumber H 8 G 8 ° lumber 8 8 G ”u“”~”””..~”..“M””“””“OO“”OO“”~OO”O“”0. January rebruary larch Apri1 SEES ““”OOOO””OO“OO”OC”OO......“OOOO st September October love-bar December total Av. ......”OOOOOC“ 257 20h 2G9 246 126 159 189 §§§§§ N 89 \l ”O.”“”CO””OO“””NOO””~00”OOOOOO””“...... 23 \o 178 135 lbs 132 86 117 132 135 136 162 165 1&9 1672 139 199 175 208 207 117 133 160 175 168 179 158 183 2062 ......”“OO”00.0””..“””“”00””””“””“ 8 172 ”“”OO”O.””””~”“”“n~””“””“00”“””0O. ...; PM 00 coax 130 108 11“ 106 91 118 115 111 122 107 103 8 number 8 H 8 G 8 8 8 1h 8 l9 8 8 8 13 8 l7 8 8 8 16 8 l3 8 8 8 lb 8 11 8 8 8 6 8 7 8 8 8 3 8 h 8 8 8 3 8 9 8 8 8 u 8 7 3 8 8 2 8 6 8 8 8 0 8 7 8 8 8 5 8 6 8 8 8 9 8 8 8 8 8 89 8 lib 8 8 8 7.8 8 9.5 8 8 77.5873.0 8 85.8877.0 8 83.5878.6 8 8h.1880.3 8 92.9893.0 83.6:77.8 mi...» 83.7:8h.b 82.8:8l.6 81.7:75.3 7h.5:6h.8 8 78.2869.l 8 - 3 .- 8 82.7878.“ 5.8 6.“ 5.7 f’ \n 1.9 1.6 1.9 1.0 0.0 2.5 U e m 8‘ s: 3 10o? 8 8 12.6 8 8 9.0 8 8 8.3 8 8.1 8 8 3.8 8 8 6.8 8 8 5.2 8 8 b.1 8 8 h.3 8 3.6 8 8 5.h x - 8 8 6.8 8 - 46 - ". P. hi ‘: :v “1 6+ “2+ '8‘ U} C‘ =4 U 1 fl? ”9 .8 1 \p ,- *. ' ' g, h .3 3 b is r. .. ;; (3‘ 8 ‘ '. i’ ‘ ’ " 1 3 w‘ 3 :3 “ ~ . ' f ,9 r .\ 8“ 1, \ 3 s a 1 '1' .. fl 7, 4 a s 3 r“ : i . V. .e~cent o: cai18:t_on: oh: 9; ' z": '3 ".4 3.1 t 1, J {:1 ' " . 19"" in. l —. -z.7_ O O L: 0 o (8' ‘1 n F6111: U m .m- 8") 1) . ‘P .‘J ‘1 I") ‘3 (11 ‘4 f’ _ i 8" fl} ‘1 a) J -na- r 8 ' 8 cf 4» 11? C‘ I :~_ ~ -. ... ~, w e I 8e . s ' t-‘ 3 ." . ’ L ... L J 8;] ' , ('1 O -:4 8:) ;.; 'Q (J) H 1 ya ' ‘8 1') n! l} e 8' ‘ r” 1 . (W 3 ., . . J ) (A? ' '1 \I r. f: v -Q- N ) f] v! 5-3 ‘4 ' u ‘ p - <2 I 4 1’ - '1 8 - " 78': 8 i - ‘ " « ‘ 4's. ~. 8 1‘ A LLsu“: r)- J‘-8-1"'.‘ A. .1 '1'.- D”7.‘qv" ..‘p -ng- TAIL! XIII. COLLECTION DATA SUMMARIED BY SEASOI : : : : : : lumber : lumber : lumber : Percent : Percent : Attegted : Shipped : Iailnres : Shipped : Failure! :_§ : G : L: G : H : G: H : G : 4!: : G : : : : : : : : : : Vinter : 695 : 1162 z 557 : 33? : 36 : 1m : 80.1: 72.9: 5.2 : 9.5 : : : : : : : : : : Spring : 621 : 363 : 532 : 300 : 36 : 31 : 85.7: 82.6: 5.8 : 8.5 : : : : : : : : : : Summer 8 557 : 381: : 468 : 319 : 10 : 20 : 81+.0: 83.1: 1.2 : 5.2 : : : : : : : : : : l‘all : 631+ : #63 ': 505 : 3&0 : 7 : 19 a 80.0: 73.1}: 1.1 : 1L1 : : : : : : 8 8 8 8 Breeding Results A summary of the numbers of cows bred monthly and seasonally and the breeding results may be found in Tables XIV and IV. me percent of 30-60 day non-returns is also shown graphically in Iigure 9. The Holstein bulls maintained a considerably higher breeding efficiency than the Gnerneeys. The percent of non-returns for the Holstein breed was much higher during the spring than baring the other seasons. The Guernseys appeared to be at peak efficiency in the fall. The months of the highest percent of non-returns were March and April for the Holsteins. The Guernseys were at their highest levels in larch. October and lovember. The percent of non-returns for both breeds fell sharply in December. July was the month of lowest efficiency for the Guernseys and Docember the lowest month for the Holstein bulls. An analysis of variance showed significant differences between the Holstein bulls in percent of non-returns. The variation between the Guernsey bulls was highly significant. Although there was a monthly variation in percent of non-returns, statistica1 SIMMARY 0? MONTHLY BREEDING DATA TADIJ XIV . 3 9 8 u. 2 O 1.. 6 5 6 7 1 1 e e e e e e e 0" e A‘s 9m e . 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(f p.“ _l ‘1 o 3 TD 4 'J :1 Fig. 9. Percent of 88-60 Do? Yin-Defnrws -52.. TADDE IN. SUMMARI OI SEASONAL BREEDING DATA : : : : Number of : lumber of 30-60 : Percent of : Cows Bred : Returns : Non-return! : H : G : g. : G : .H : G : : : : : : Iinter : 6721 : #03“ : 2378 : 1701 : 6h.5 : 57.8 : : : : : : spring : 6578 : 3958 : 2118 : 1591 : 67.5 : 59.5 : : : : : : Summer : 8851 : 3296 : 175k : 1389 : 6h.4 : 57.9 : : : : : : Pall : #106 : 2&2? : 11+32 : 9+1 : 65.1 : 61.3 : : : : : : analysis showed it to be not significant. lffect of Light and Teggerature on Breeding Results A statistical analysis of the effects of light and temperature on the percent of non-returns failed to show any significant correlations when the two are considered together. Partial correlations, however, show that light from the first previous month had a highly significant negative correlation (P = - 0.83“) with the percent of non-returns for the Guernsey bulls. The correlation was significant for the Holstein sires (P - - 0.730). Partial correlations in which the light of the previous month was eliminated and only the current temperature considered showed the temperature effect on fertility to be essentially as great as the delayed effect of light but of positive effect. The correlation coefficients were. Guernseys P c 0.827 and Holsteins P = 0.722. These were highly significant and significant. respectively. DISCUSSION lens of the semen characteristics studied in this investigation (volume. concentration, total spermatozoa, and initial motility) were significantly correlated with fertility. Previous workers hare reported varying results. Anderson (2) found volume, concentration and initial motility to be related to fertility. Lasley and Bogart (#1) correlated volume. concentration and total sperm but not initial motility, with fertility. Swanson and Herman (80) found nun-.1 motility but not concentration to be an index of fertility. lercier and Salisbury (#7) state that concentration is a guide to breeding results. Daugherty and Ewalt (28) and Swanson and Herman (79) were unable to establish any relationship between concentration. initial motility or volume and fertility. It is not unlikely that some of this variability of results stems from the standards required of the semen.before it is used for inseminatian. Semen abnormally deficient in any quality will not give as good breeding results as that which is normal. Ihen semen is selected for field‘use in artificial insemination it usually must meet certain minimum standards in several of the measures of semen quality. It is probable that these minimum specifications are set at levels above which quality variations are not important in determining fertility. then the standards are lowered or un- selected semen is used semen quality may be enacted to be more highly correlated with fertility. The variation in reported relationship of semen quality does. however. indicate the desirability of a single measure of semen quality highly corre- lated with semen characteristics and fertility. - 5n - Investigations by Anderson (3), Rape and Cannon (60) and Reid and associates (62) indicated that determination of the semen pH either initially or the drop in pH after incubation for one hour at “0° 0. may be a desirable method of indirectly determining semen quality. It has the advantage of requiring little specialized equipment or training. Considerable variation in semen quality was observed between bulls of the same breed and between breeds in this investigation. Similar find- ings have been.published byilercier (b6) and Hercier and Salisbury (47). Seasonal trends in spermatogenic activity of the bulls were also found. In general the semen was of higher quality during the spring and summer than during the fall and winter. However, the monthly variations were not t statistically significant. The diversity of results obtained by other investigators, (2h) (25) (29) (30) (31) (36) (#8) (b9) (50) (51) (55) (7h) (75) (81) (90). indicate that seasonal trends vary with the geographical location of the bulls under study. Hercier and Salisbury (#8) (#9) have concluded that light is one of the manor climatic factors affecting spermatogenesis. Statistical analysis of their data also indicated a lag of about one month before the maximum response to light variation was reached. The results of this study also in- 1 dicate that light variations are more important than temperature effects in ”- influencing spermatogenic activity. However, the delayed effect of light reported by Hercier and.Salisbury was not evident in so far as its action on semen.quality was concerned. Partial correlations to determine the effect of light and/or temperature alone indicated that neither of these factors by itself is as effective as -55- the two working together. It is appreciated that the percent of 30-60 day non-returns is not a desirable measure of bull fertility. As Casida.and associates (22) have indicated,‘use of this fertility index introduces approximately a.fifteen percent error into the fertility data. However, records of the association did not permit use of a longer time. It is believed too that while more accurate fertility data might have changed the individual figures the trends observed would have remained the same. Highly significant differences in fertility of individual bulls were found. A.breed difference in fertility level was also evident. However. the monthly variations in.percent of non-returns was not significant. These results are in accord with those reported by Salisbury (71). A breed difference in seasonal trends was observed. The Holstein bulls were of highest fertility during the spring and lowest in winter and summer. The Guernseys'were also of low fertility during the winter and summer but peak fertility came in the fall. hills of both breeds tended towards more prompt service of the cows during the summer and fall months. It is likely that the longer hours of daylight and.higher temperatures act as stimuli to libido in bulls. A breed difference and a seasonal variability in the percent of collection failures were also found. A.greater percentage of Guernsey bulls either refused to serve or were unable to ejaculate semen. The percentage of such failures was lower in the summer and fall than during the other months for both breeds. The observed superiority of the Hblstein bulls in fertility and some -55- semen characteristics is similar to the findings of Mercier and Salisbury (#7). In view of the difference in fertility level observed between the Holsteins and Guernsey breeds it is interesting to note the difference in pH of the semen of the two breeds. Rape and Cannon (60) found that the semen of Holstein bulls was more acid than that of Guernsey bulls. This may be one of the factors responsible fer the lower fertility of the Guernsey bulls. It is unlikely that the superiority in semen quality observed here entire- 1y accounts for the fertility differences between the breeds. The semen used for insemination was selected in both cases. At times the standard of quality for shipment of Guernsey semen had to be lowered due to the low quality of the semen produced and the necessity of using some of it for breeding purposes. It is believed, however, that at no time was the quality of the semen shipped low enough to affect breeding results. The findings of this study confirm the earlier report of Mercier and Salisbury (#9) in so far as noting a lag before the maximum effect of light variation upon fertility is concerned. Hercier (#6) found a difference in response to light and temperature variation.between bulls kept in.lew York State and those in Eastern Canada. Both temperature and light were negatively correlated with fertility of bulls used in artificial insemination in New York State. under natural breeding conditions in Eastern Canada both factors were posidvely correlated with breeding results. The data shown here indicate that under South Central Michigan conditions . bull fertility is negatively correlated with.light and positively correlated : with temperature. The influence of these variables appears to be of the same magnitude. These results would.indicate that factors other than light and temperature cause the observed variations in fertility within breeds. -57- Ihe suggestion is offered that in other geographical locations where either temperature or light may vary considerably more than in.lichigan, one or both of these factors maybe of greater importance in influencing spermatogenesis and fertility of dairy bulls. the differences fbund in reports of seasonal fertility my thus be explained. 3. 5. 6. 7. SUMMABI Records of semen.production and breeding results of 20 Holstein and 17 Guernsey bulls used in artificial insemination during a 35 month period were analysed. Over h,000 semen collections and 107.000 breeding records were tabulated in this study. Significant or highly significant correlations for one or both.breeds were obtained.between volume and total spermatosoa per ejaculate. volume and initial motility. concentration and total spermatosoa, con- centration and initial motility, and total sperm and initial motility. Highly significant differences between bulls of the same breed were observed in every semen characteristic studied. A.brsed difference in semen volume. concentration and initial motility was evident. Honthly variation in semen quality was not significant although the quality was higher in the spring and summer than during the fall and winter. Light and temperature were both positively correlated.with spermatogenesis. Light appeared to exert the greater effect. ’"u lo significant correlations between variations in semen selected for shipment and actual fertility were found. 9. 10. 11. 12. 1h. - 59 - Libido of bothbreeds appeared to be highest in the M. Fertility of the Holstein bulls was consistently higher than that of the Guernsey bulls. Highly significant fertility differences were observed.between bulls. Fertility of the Holstein bulls was highest during the W. The Guernsey bulls were of highest fertility in the fall. Monthly variations in fertility of either breed were not statistically significant. A negative effect of light on fertility was noted. The maximum effect was after one month lag. a.positive effect of current temperature on fertility of the same magnitude as the light effect was found. v. e,“' ..I (1) 9(3) (4) (5) (6) (7) (8) (9) (10) <11) BIBLIOGRAPHY Anderson, J. 1936 Studies on reproduction in cattle II. Emp. Jour. Expt. Agr. 1+: 197-207. l9h0 Investigations on the semen of fertile and sterile bulls. Vet. Jour. 96: 18-27. 1942 The clinical significance of the hydrogen-ion concentra- tion of the semen of the bull. Yet. Record 54: 317-318. 1905 The semen of animals and its use for artificial insemina- tion. Imp. 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