James Graham, PhD, of Colorado State University, spoke in the Reproduction session at the Nov. 2001 convention of the American Association of Equine Practitioners. In this presentation he said many attributes other than motility are involved in a sperm’s good health and fertilizing capability. "If we look only at motility," he said, "we will over-estimate fertility."

Available to the practitioner are laboratory assays that can help pinpoint problems with infertile sperm. Included are:

1. Computer-assisted sperm analysis systems that permit the accurate evaluation not only of the percentage of motile sperm, but also percentages of progressively motile cells and the velocities of the motile sperm.
2. Fluorescent stains that provide greater contrast between "live" cells and "dead" cells. "Recent developments in flow cytometry and fluorometry make viability assessments rapidly and inexpensively."
3. Fluorescently labeled stains that can be used to visualize the stallion sperm acrosome and assess whether it is capable of functioning normally.
4. Light microscopic evaluation of stained or unstained sperm that can be used to assess sperm to determine whether it is normal.
5. In vitro assays to determine the ability of spermatozoa to undergo capacitation and the acrosome reaction.

Graham concluded his presentation by saying, "Laboratory assays have been developed which evaluate multiple sperm parameters on large numbers of sperm in a semen sample. These assays may prove useful in evaluating semen prior to insemination or at the beginning of the breeding season. They will also be invaluable in developing new techniques for preserving stallion semen.

"Although the ability of these assays to predict fertility has not been established, recent data indicate that utilizing several assays that evaluate different attributes of the spermatozoa can be highly correlated with stallion fertility