In the case of pregnancy, the uterus and the embryo send hormones that help maintain the corpus luteum throughout the entire pregnancy. The testes of the bull produce the male sexual cells or spermatozoa which, like the egg, contain only one copy of the genetic information necessary to constitute an individual. The scrotum is the sack located outside the abdominal cavity that contains the testes. By adjusting the distance between the testes and the body, the scrotum regulates the temperature of the testes. This is necessary because the formation of spermatozoa functions better at a temperature 2 to 4C lower than normal body temperature.
Some bulls have only one testis in the scrotum.
This descended testis will function properly, but the one that remains in the body cavity will not. This condition is inherited and these bulls should not be used so the propagation of this defect will be avoided. Each testis is enveloped in its own compartment and each is a complete, independent unit. At the time of mating, before the sperm is ejaculated, the spermatozoa are mixed with secretions rich in nutritive substances from the secondary sex organs. Thus symptoms of bull infertility may occur two and a half to three months after the process of sperm formation has been impaired.