Stallion semen is particularly susceptible to freeze-thaw damage, so multi-step procedures are being developed and evaluated to slowly extend and cool the semen prior to freezing it. In addition, the common semen extender INRA82, developed at INRA-Haras Nationaux in Nouzilly, France, is being modified with various additives in an attempt to improve it. A series of experiments was recently conducted in Nouzilly to evaluate the effects of INRA82 with various additives in differing conditions on stallion sperm motility and fertility.

The first experiment demonstrated no advantage to collecting the sperm-rich fraction versus the entire ejaculate in terms of motility in either fresh, cooled, or frozen semen. An additional experiment examined both temperature and extender additives, demonstrating no statistically significant difference in motility whether thawing was performed at 71.6ºF (22ºC) in extender with egg yolk and glycerol or at 98.6ºF (37ºC) in extender with egg yolk only. Changing the concentration of egg yolk from 2-4% had no effect on post-thaw motility. There was some improvement, although only slight, with extender containing glycerol, but only in certain stallions.

Amino acids were also tested in the extender, and glutamine (50mM) improved post-thaw motility, although only in stallions with initially poor motility. Addition of the stain Concanavalin A was also evaluated, because previous reports indicated it could coat spermatozoa heads and protect them during freezing. Unfortunately, no such protective effects were seen in this study. So, these results indicate that while INRA82 can be improved with additives, more work needs to be done to optimize this extender for use with stallion semen.

Vidament, M.; Yvon, JM.; Cout, I. et al. Animal Reproductive Science, 68, 210-218, 2001.

About the Author

Susan Piscopo, DVM, PhD

Susan Piscopo, DVM, PhD, is a free-lance writer in the biomedical sciences. She practiced veterinary medicine in North Carolina before accepting a fellowship to pursue a PhD in physiology at North Carolina State University. She lives in northern New Jersey with her husband and two sons.

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