Evaluation of stallion semen.

This article outlines a basic method for conducting a stallion semen evaluation. After the removal of the gel fraction of the ejaculate, semen gel-free volume is determined, and any abnormality in appearance is noted. Concentration of sperm cells in semen can be determined with the use of either a hemacytometer or spectrophotometer after appropriate dilution of raw semen. The percentage of progressively motile sperm is evaluated promptly after collection of semen with the use of a phase-contrast microscope. The total numbers of sperm and progressively motile sperm in the ejaculate are calculated. The determination of seminal pH and the classification of sperm morphologic features are additional seminal characteristics evaluated during a semen evaluation. Sperm motion characteristics can be further evaluated with the use of computerized sperm image analysis systems and may add additional information concerning the quality of ejaculated sperm. Unfortunately, no single seminal characteristic has in itself been shown to be highly correlated with fertility, although various seminal characteristics are known to affect fertility. Therefore, to properly interpret the fertility of a semen sample, a complete and thorough semen evaluation must be performed.