Relationships between growth parameters and scrotal circumference in young beef bulls

Abstract

Scrotal circumferences of 119 young bulls of four distinct breeding groups were measured at the end of a feedlot performance test and at the beginning of the breeding season when the bulls were approximately 14 months old, to study the relationships of weight and growth parameters with testes size. Scrotal circumference was positively correlated with body weight at the end of feedlot test in the four breeding groups. The association between scrotal circumference and body weight was much stronger in the breeding group which had been selected for low yeariing weight than in the other three breeding groups which had been selected for high growth rate. The relationships between scrotal circumference and preweaning and postweaning gain differed among the four breeding groups. Preweaning gain was the most important factor in the association between body weight and scrotal circumference among the three beef breeding groups. The results indicated that the preweaning stage was a critical period for testicular development and that the probability of finding beef bulls with smaller than average testes among the bulls selected for weaning weight would be relatively small. Scrotal circumference was reduced (2.5–11%) from the end of feedlot test until the beginning of the breeding season.