TESTICULAR DEVELOPMENT OF SALERS BULLS TO ONE YEAR OF AGE

Transcription

1 NOTES TESTICULAR DEVELOPMENT OF SALERS BULLS TO ONE YEAR OF AGE Scrotal circumference measuremen$ were mken on 255 Salers bulls located at five growth performance test stations at the 56-d ( cm), 84-d ( cm) and 140-d weighings ( cm) in 1986, and on248 Salers bulls located at four test stations at the 140-d weighing ( cm) in The estimated scrotal circumference measurement for Salers bulls at 365 d of age was 29.4 cm. Test station, percentage of Salers breeding within test station, sire ofbull within year and test station, and the covariate body weight all contributed to the variance in scrotal circumference measurements. Incorporation of sire of bull within year and test station into the statistical model accounted for a much higher proportion of the variance in scrotal circumference measurements (f : 65%) than when percentage of Salers breeding within test station was substituted, G : 32%). Key words: Testicular development, scrotal circumference, Salers bulls, recommendations [D6veloppement testiculaire de taureaux Salers i I'dge d'un an.] Titre abr6g6: Des mesures de la circonf6rence du scrotum ont 6t6 faites sur 255 taureaux Salers situ6s dans cinq stations d'6preuves aux pes6es de 56 jours (26,9 + 0,2 cm), 84 jours (28,8 + 0,2 cm) et 140 jours (30,8 + 0,2 cm) en 1986, et sur 248 taureaux Salers situ6s dans quatre stations d'6preuves ir la pes6e de 140 jours (31,3 + 0,1 cm) en La mesure estimative de la circonf6rence du scrotum des taureaux Salers d I'Age de 365 jours estde29,4 cm. La station d'6preuves, le taux d'ascendance Salers par station d'6preuves, le pdre du taureau par ann6e et station d'6preuve et le poids corporel ont tous contribu6 ir la variance des mesures de Ia circonf6rence du scrotum. L'int6gration du pdre du taureau par ann6e et station d'6preuves au moddle statistique reprdsente une bien plus grande proportion de la variance des mesures de la circonf6rence du scrotum Q2 : 65%) que le taux d'ascendance Salers par station d'dpreuves (f : 32%). Mots cl6s: D6veloppement testiculaire, circonf6rence du scrotum, taureaux Salers, Salers cattle were introduced into a";;t"'01;:o"ro"se of rhis srudy was to describe Althoughnumbersof Salerscattlehave the testicular development of young Salers increased rapidly to a total of about bulls to l-yr ofage and to identiry factors that registrations by the end of 1986, very little influence the rate of testicular growth of data are available on the testicular develop- young Salers bulls during 140-d growth ment of Salers bulls in Canada. Testicular size performance tests. inbeef bulls, asmeasuredby scrotalcircum- Salers bulls (n : 255) located at five ference, is associated with puberty in the bull growth performance test stations, Cattleland (Lundstra et al. 1978), the quantity of sperm- Feedyards Limited, Strathmore, Alberta producing tissue (Coulter and Keller 1982), (n : 87), Highway No' 52 Feeders, seminal quality (Cates 1975), age at puberty Raymond, Alberta (n : 43), Saskatchewan (Brinks et al. 1978; King et al. i983; Toelle Livestock Centre, Regina, Saskatchewan and Robison 1985) and fertility of female pro- (n : 4l), Gerald Dixon's, Carstairs, Alberta geny (Toelle and Robison 1985). Because of (n : 33), and Coldstream Ranch Limited, these important relationships, it is desirable Vernon, British Columbia (n : 51) wereused to characterize the testicular development of in the study during the winter and early spring bulls in a breed. of Scrotal circumf'erence measurements were taken within 2 d of the 56-, 84- and Can. J. Anim. Sci. 68;96r-964 (Sept. 1988) 140-d weighings at all test stations. No scrotal 961

2 962 CANADIAN JOURNAL OF ANIMAL SCIENCE crrcumlerence measurements were taken at the 56-d weighing at the Gerald Dixon test station. In addition, Salers bulls (n : 248) located at the first four growth performance test stations (n : 151, 34, 3l, 32, respectively) had their scrotal circumferences measured at the time of the 140-d weighing in the early spring of All scrotal circumference measurements were taken by one technician using the measurement technique recommended by the Society for Theriogenology (Ball et al. 1983). Three separate statistical analyses were conducted on these data. First, separate anlayses of variance (Statistical Analysis System Institute, Inc. (SAS) 1985) were conducted for scrotal circumference measurement data taken at three dates (56, 84 and 140 d on tesr) at five test stations during Effects of test station (I, 2,..., 5), either percentage of Salers breeding within test station 13lt,1la, purebred and fullblood) or sire of bull within test station (I, 2,.., n), two-way interactions, and the covariate body weight were examined. Percentage of Salers breeding and sire of bull could not be included in the same model as both were nested within test station necessitating the examination of separate models for each factor. Second, analyses of variance (SAS 1985) were conducted on scrotal circumference measurements taken at four of the test stations at the 140-d weighing in both 1986 and 1987 (n : 450). Data from bulls measured at Coldstream Ranch Limited at the 140-d weighing in 1986 were deleted from this analysis as bulls at that station were not measured in Effects ofyear (1986, 1987), test station (1,...,4), either percentage ofsalers breeding within test station or sire of bull within year and test station, two-way interactions, and the covariate body weight were examined. Sufficient records were not available to determine either age of dam effects or herd of origin within test station effects on scrotal circumference measurements. Although bull age was an important factor (P < 0.01) influencing scrotal circumference measurements when considered independently, this effect was reduced (P > 0.05) when body weight was also considered. Therefore, bull age was removed from the statistical models. Multiple regression analyses (SAS 1985) were applied to scrotal circumference measurement data to estimate the best fitting curve where scrotal circumference measurements were adjusted for bull age, a quadratic term for bull age, year, test station, and sire of bull within year and test station. This curve was used to estimate scrotal circumference measurement at 365 d of age. The mean ages of bulls in the hve test stations in 1986 at the 56-, 84- and 140-d weighings were ,331 * 2, and 386 * 2 d. The corresponding body weights were , , and508 t 3 kg. Theleast squares mean scrotal circumference measurements at these ages and weights with sire of bull in the model were , , and cm. Between the 56- and 84-d weighing the scrotal circumference of Salers bulls increased at about twice the rate (1.9cm over 30d) compared with the increase in scrotal circumference between the 84- and 140-d weighings (2.0 cm over 55 d). Significant variation in scrotal circumference measurements occurred among the participating test stations in The effect of test station increased as the growth performance test progressed. At the 56- and 84-d weighings there were no effects (P > 0.05) of test station, but test station was significant (P < 0.05) by the end of the 140-d test. The effect of test station on scrotal circumference measurements may have resulted from variation in diet among test stations. Digestible energy content of the diet fed to bulls at the test stations during the last part of the 140-d test ranged from ll.464 to MJ kg - t. There appeared to be a direct relationship between level of energy fed and scrotal circumference measurement in four of the five test stations. Angus and Hereford bulls fed diets with high versus medium levels of energy during a 168-d growth performance test had greater scrotal circumference measurement at I yr of age, demonstrating a

3 COULTER AND BAILEY - TESTICULAR DEVELOPMENT OF SALERS BULLS 963 potential effect of diet on scrotal circumference measurement (Coulter et al. 1987). The effect of feeding varied levels of dietary energy on the reproductive capacity of bulls ofthe Salers or other Continental breeds is unknown. Percentage of Salers breeding affected scrotal circumference at 56 (P < 0.05), 84 and 140 d (P < 0.01) on test: however. the effect was not consistent among test stations resulting in a test station by percentage of Salers breeding interaction (P < 0.05). As a result, a clear statement of the effect of percentage Salers breeding on scrotal circumference measurements cannot be made. No biological reason is known for percentage of Salers breeding affecting scrotal circumference. The genetic contribution by breeds in the non-salers portion may influence scrotal circumference. When percentage of Salers breeding was replaced by sire ofbull, it also had a significant effect on scrotal circumference measurements at 56 (P < 0.01), 84 and 140 d (P < 0.05) on test. Sire of bull within test station accounted for a higher proportion ofthe variance in scrotal circumference measurements than percentage of Salers breeding within test station. The r2 for models incorporating sire of bull within test station versus percentage of Salers breeding within test station at each of 56, 84 and 140 d was 76 vs. 43, 72 vs. 44 and 67 vs. 32%, respectively. Body weight was an important factor contributing to the variance in scrotal circumference measurements of Salers bulls at all three measurement times. Heavier bulls that were usually older generally had greater scrotal circumferences. Salers bulls completing their 140-d growth performance test at four test stations in 1986 and 1987 at 383 * 1 d of age had a mean body weight of kg and scrotal circumference measurement of 31.0 * 0.1 cm. When percentage of Salers breeding within test station was introduced into the model, it accounted for a smaller proportion of the variance (fr : 32%) than when sire of bull within year and test station was substituted (f : 65%). When percentage of Salers breeding within test station was used, test station had a significant effect on scrotal circumference measurements both in 1986 (P < 0.01) and 1987 (P < 0.05). A year by percentage of Salers breeding within test station interaction (P < 0.05) was also noted. The percentage of Salers breeding within test station contributed (P < 0.01) to the variance in 1986, but not in 1987 (P > 0.05) indicating that true differences in scrotal circumference measurements due to the percentage of Salers breeding must be questioned. When sire of bull within year and test stiation was substituted into the model, a year-by-test-station interaction (P : 0.05) occurred because of an effect of test station in 1986 (P : 0.01) that disappeared in 1987 (P > 0.05). Sire of bull within year and test station contributed (P < 0.01) to the variance of scrotal circumference measurements in both years. Substitution of sire of bull into the model for percentage of Salers breeding appears to be superior. In all models considered, the covariate body weight had an effect (P ( 0.01) on scrotal circumference measurements. This is consistent with the f,rndings reported by Coulter and Keller (1982). An estimated scrotal circumference measurement of 29.4 cm for Salers bulls at 365 d of age was obtained using the best fitting multiple regression equation: Y : 22.t G ()P) where Y is scrotal circumference in centimeters adjusted for sire of bull within year and test station and X is bull age in days. Both linear (P < 0.05) and quadratic (P : 0.06) terms were significant. The moderate 12 value of 59% is indicative of the variation in the scrotal circumference measurements of Salers bulls. A higher I value would not be expected considering the relatively narrow age range ( d) over which the regression equation was calculated. The estimated mean scrotal circumference measurement of 29.4 cm for Salers bulls at 365 d of age is similar to that reported for the Limousin and

4 964 CANADIAN JOURNAL OF ANIMAL SCIENCE Blonde d'aquitaine breeds and is relatively small compared with most major beef breeds (Coulter and Keller 1982) when using the same scrotal circumference measurement technique (Coulter et al. 1986). Scrotal circumference measurement is a good predictor of puberty in the beef bull (Lundstra et al. 1978). Adjustment of scrotal circumference measurements for age rather than for body weight is recommended. Beef bulls are generally first introduced into breeding programs as yearlings. It is desirable for cattlemen to use bulls that reach puberty early, are suitable for breeding at a young age, and transmit early puberal characteristics to their progeny, particularly the females. Further, body weight is subject to the influences of the environment, while age is not. We wish to acknowledge the financial support of the Salers Association of Canada and to thank the management and contributors of the bull test stations listed for their assistance and cooperation. Ball, L., Ott, R. S., Mortimer, R. G. and Simons, J. C Manual for breeding soundness examinations ofbulls. Soc. Theriogenol. 12: Brinks, J..S., Mclnerney, M. J. and Chenoweth, P. J. f978. Relationship of age at puberty in heifers to reproductive traits in young bulls. Proc. West. Sect. Am. Soc. Anim. Sci. 29: Cates, W. F Observations on scrotal circumference and its relationship to classification of bulls. Pages 9-27 in Proc. Annu. Meet. Soc. Theriogenology, Cheyenne, Wyoming. Soc. Theriogenology, Hastings, Nebraska. Coulter, G. H., Carruthurs, T. D., Amann, R. P. and Kozub, G. C Testicular development, daily sperm production and epididymal sperm reserves in 15-month-old Angus and Hereford bulls: Effects of bull strain plus dietary energy. J. Anim. Sci. 64: Coulter, G. H. and Keller, D. G Scrotal circumference of young beef bulls: Relationship to paired testes weight, effect of breed, and predictability. Can. J. Anim. Sci. 62: Coulter, G. H., Mapletoft, R. J. and Kozub, G. C Effect of measurement method. breed. and technician on scrotal circumference measurements. Can. J. Anim. Sci. 66: King, R. G., Kress, D. D., Anderson, D. C., Doornbos, D. E. and Burfening, P. J Genetic parameters in Herefords for puberty in heifers and scrotal circumferences in bulls. Proc. West. Sect. Am. Soc. Anim. Sci. 34: Lundstra, D. D., Ford, J. J. and Echternkamp, S. E Puberty in beef bulls: Hormone concentrations, growth, testicular development, sperm production, and sexual aggressiveness in bulls of different breeds. J. Anim. Sci. 46: to54-t062. Statistical Analysis System Institute, Inc SAS user's guide; Statistics Version 5. SAS Inc., Cary, N.C. Toelle, V. D. and Robison, O. W Estimates of genetic correlations between testicular measurements and female reproductive traits in cattle. J. Anim. Sci. 60: G. H. COULTER and D. R. C. BAILEY Research Station, Agriculture Canada, Lethbridge, Alberta, Canada TIJ 4Bl. Received 10 Feb. 1987, accepted 2 Mar

5 This article has been cited by: 1. E. Pereira, J.P. Eler, F.A.A. Costa, J.B.S. Ferraz Análise genética da idade ao primeiro parto e do perímetro escrotal em bovinos da raça Nelore. Arquivo Brasileiro de Medicina Veterinária e Zootecnia 53:1, [Crossref]