Larger Scrotal Circumference Research Articles

Effect of energy intake after weaning on the sexual development of beef bulls. II. Age at first mating, age at puberty, testosterone and scrotal circumference.

Simmental and Hereford bulls were individually fed varying levels of the same diet to determine the effect of energy intake after weaning on rate of sexual development. For 200 d, 29 Simmentals were fed an average of 14.6, 19.2 or 23.8 Mcal and 27 Herefords were fed 13.4, 17.5 or 22.2 Mcal metabolizable energy per bull daily. Higher energy did not hasten sexual development, as measured by serum testosterone, age at first mating or age at puberty. As energy level increased, weight at puberty increased (P less than .05) for both breeds, and scrotal circumference at puberty increased (P less than .05) for Simmentals. When adjusted for breed and energy level, bulls that were heavier at 1 yr of age had larger scrotal circumference (P less than .05) and were younger at puberty (P less than .01). Bulls that had higher serum testosterone at 1 yr of age reached puberty earlier (P less than .01). At a constant age there was no relationship between testosterone and scrotal circumference. Although higher levels of energy increased scrotal circumference of Simmentals, it did not hasten sexual development for either breed.

INFLUENCE OF BREED, BIRTH DATE, AGE AND BODY WEIGHT ON TESTICULAR MEASUREMENTS OF GROWING RAMS MAINTAINED IN A CONTROLLED ENVIRONMENT

Testicular measurements, including scrotal circumference (SC), testis length (TL), testis width (TW), scrotal skinfold thickness (ST) and tonometer score (TS), and body weight (BW) were collected from 233 rams of three synthetic strains, Suffolk and Finnish Landrace breeds, at 6, 8 and 10 mo of age, at the time of first breeding in September 1981 (11–13 mo) and second breeding in April 1982 (18–21 mo). Rams were exposed to continuous light from birth to weaning (21 ± 3 days of age), to a long day-length (16 h light: 8 h darkness) from weaning to 6 mo and then to a short day-length (9 h light: 15 h darkness) to the time of breeding. Subsequently, the rams were exposed to 4 mo of long day-length followed by a 4 mo of short day-length. All rams were hysterectomy derived, housed indoors year-round on expanded metal floors in windowless barns and reared artificially. Breed, birth date, age of ram and body weight were found to have important effects (P < 0.05) on testicular measurements of growing rams, whereas, age of dam and litter size effects were absent (P > 0.05). In general, meat-type sire breeds (Strain 1 and Suffolk) had larger SC, TL, TW and BW when compared to the fecund sheep breeds (Finnish Landrace, Strains 2 and 3). Testicular measurements and BW of Finnsheep rams were smaller when compared to all other rams examined. The significance of breed and birth date effects varied as the ram progressed in age. Testicular measurements and BW increased with age of ram from 6 to 8 mo but TS showed no change. SC and BW increased substantially at 18–21 mo (April) compared to 11–13 mo (September), whereas TL, TW, ST and TS declined. SC, TL and TW were significantly correlated with each other at all ages. ST and TS were independent traits with no significant relationship to SC, TL, TW and BW. Key words: Sheep, testicular measurements, breed, birth date, age of ram, body weight