Common causes of infertility in the bull.

Fertility is a fragile parameter that may vary temporarily or be permanently depressed. The bull's ability to maintain body condition and the existence of conformational abnormalities may alter fertility. Abnormalities of the external genitalia may directly affect the bull's ability to copulate or may alter the quality of his semen. Testicular disease alters semen quality, sometimes transiently and other times permanently. In many cases, the fertility prognosis for testicular problems cannot be judged on the basis of one examination. Epididymitis and seminal vesiculitis are the two most common diseases of the secondary sex organs of the bull. They are often associated with each other or orchitis and are difficult to treat.