Development of testicles and sperm production in bulls used in Bryanskaya oblast' in connection with growing intensity

The changes of testfcles in connection with different growing intensity and keeping conditions were investigated in bulls of the Black-and-White breed at the period from the birth to 18-month-old. The indices of sperm production were estimated in bull-sires of the Black-and-White breed at the age from 16 to 100-month-old. It was shown that the testicles grow more actively at the first 10-12 months of animal live. During the moderately-high intensity of growing the bull-sires have low level of sperm production, but during moderately-high and high - the duration of bull use is reducing.