After the scrotum is measured, the testicles and epididymis are palpated for swellings and the penis is checked for abscesses, adhesions and penile deviations. To ensure nothing is missed, the penis should be evaluated before and during erection. Finally, semen is collected and evaluated for volume, colour, mobility and morphology. Volume will vary but, like circumference, a minimal amount is needed for successful insemination. Colour can be a good indicator of quality.
Healthy semen is milky white.
Discolouration due to blood or pus indicates a problem. Motility of sperm cells is determined by putting a drop of semen on a slide. Morphology is an assessment of sperm cell appearance. High numbers of abnormally formed sperm are associated with poor conception rates. Bulls should be assessed each year because they can pick up infections and have injuries that only show up in the next breeding season.