Bull Development (in Utero to One Year of Age)

Abstract

Age at puberty has a profound effect on the efficiency of cattle production. Since one bull is typically responsible for impregnating multiple females, understanding pubertal changes and factors affecting reproductive development and function in bulls is vitally important. There is a well-documented series of events in development of the testes and establishment of spermatogenesis. Although semen quality and fertility are below minimum standards at puberty (defined as > 50 x 106 sperm and > 10% motility), both improve rapidly within a few months thereafter. Nutrition when the bull calf is in utero, and particularly after birth, has a profound effect on reproductive development. In particular, bulls that are very well fed prior to six months of age had earlier puberty, larger testes, and produced more sperm than those with restricted nutrition during this interval. After six months of age, bulls should be fed an adequate diet, as overfeeding will not overcome previous nutritional deficits, and will generally have adverse effects of semen quality and sperm production. [...]