Ancillary tests of bull semen quality.

Seminal quality examinations readily identify animals with low fertility, but rarely can these tests discriminate among males with moderate to high fertility. The new, automated semen analysis systems tend to be helpful in providing more reliable information. Such systems, especially the CASA systems that assess sperm morphology and motility, are innovative and certainly attractive. They may not, however, be cost effective. Similarly, although the combination of fluorescent staining and flow cytometry offers a very rapid and precise means of assessing the functional status of sperm organelles, it tends to be relatively expensive as a clinical tool. Such automated sperm quality assessments will likely become routine analyses at the larger semen-processing organizations. However, the true success of a breeding program can only be assessed by the number of live offspring. Thus, determination of true fertility, because of the complexity of the processes that unite the gametes, will continue to require more than a detailed examination of seminal cytology, no matter how sophisticated our methods become.