Injury and disease to the penis is observed and the testes and epididymis are palpated for evidence of degeneration or inflammation. Scrotal circumference is measured and is a good indication of semen producing ability. Larson says all testicles produce the same number of sperm per gram of testicle. Thus, a bull with bigger testicles will produce more sperm. Because of the difference among testicular sizes, daily sperm production among bulls varies from three billion to more than eight billion.
Research shows increased scrotal circumference also relates to earlier puberty in daughters.
After the physical examination and scrotal measurement, a semen sample is collected either with the aid of an electro-ejaculator, massage of the prostate or use of an artificial vagina and a mount animal. The sperm sample is evaluated for sperm motility and for the presence of excessive numbers of abnormal sperm. The breeding soundness exam is a pass-fail test and one bull does not score higher than any other bull that passes the test. If a bull fails any part of the exam he fails the entire test. For example, if a bull has excellent scrotal circumference and excellent semen motility, but has a rear leg conformation that limits his ability to cover a breeding pasture, he fails the examination and is not considered a satisfactory breeder.