Relationships Among Scrotal Circumference and Certain Performance Traits of Beef Bulls During Postweaning Feedlot Performance Tests

Abstract

Knowledge of the relationships between scrotal circumference and performance traits can give cattlemen important information for selecting superior sires. Data were collected from 673 individually fed bulls in the University of Arkansas beef-bull performance tests from 1983 through 1986 to evaluate these relationships. Three Arkansas locations, including Fayetteville (1 test/yr), Monticello (1 test/yr), and Hope (2 tests/yr), and 10 breeds were included in the analysis. The dependent variable, scrotal circumference (SC), was analyzed using a model including test number, breed, initial weight (WTI), initial age, backfat thickness (BF), feed conversion (FCONV) and average daily gain (ADG). Scrotal circumference, WTI, BF, ADG, and FCONV were measured in cm, kg, cm, kg and as kg feed/kg gain, respectively. Test number accounted for the variation associated with year, location and season. Breeds evaluated were Simmental (SM), Angus (AN), Hereford (HF), Maine-Anjou (MA), South Devon (SD), Polled Hereford (PH), Charolais (CH), Santa Gertrudis (SG), Brangus (BR) and Beefmaster (BM). Least-squares means indicated that the SM bulls had larger SC (P<.05) than SD, PH, CH, SG, BR, and BM. Conversely, the BM bulls had smaller SC (P<.05) than SM, AN, HF, MA, SD, PH, and CH bulls. The partial regression coefficients of SC on WTI, BF, and ADG were .017, 1.459, and 3.328cm per unit of measurement, respectively. These data suggest that bulls that are heavier at the start of the test, have higher ADG and greater BF tend to have larger SC.