Ancillary Methods for Semen Evaluation.

The cause of subfertility or poor fertility in naturally mated bulls should be differentiated from impotentia coeundi, generandi, or erigendi prior to ancillary semen evaluation. Bulls used for artificial insemination may undergo ancillary semen evaluation following low fertility rates as judged by poor conception or low pregnancy rates. Morphologically abnormal sperm have long been associated with bull subfertility and infertility. Some morphological defects such as improper sperm chromatin condensation are not visible using traditional light microscopy and require specialized staining. Ancillary semen evaluation is useful in cases where the reason for low or absence of fertility needs to be identified. As compared to SEM, TEM can be extremely useful for identifying minuscule acrosome defects, issues with chromatin, and centrosome defects and is considered the gold standard method for the identification of midpiece and tail defects.