Effect of shortening the prefreezing equilibration time with glycerol on the quality of chamois (Rupicapra pyrenaica), ibex (Capra pyrenaica), mouflon (Ovis musimon) and aoudad (Ammotragus lervia) ejaculates

The present study reports the effect of shortening the prefreezing equilibration time with glycerol on the quality of frozen-thawed ejaculated sperm from four Mediterranean mountain ungulates: Cantabrian chamois (Rupicapra pyrenaica), Iberian ibex (Capra pyrenaica), mouflon (Ovis musimon) and aoudad (Ammotragus lervia). Ejaculated sperm from these species were divided into two aliquots. One was diluted with either a Tris-citric acid-glucose based medium (TCG-glycerol; for chamois and ibex sperm) or a Tris-TES-glucose-based medium (TTG-glycerol; for mouflon and aoudad sperm), and maintained at 5 °C for 3 h prior to freezing. The other aliquot was diluted with either TCG (chamois and ibex sperm) or TTG (mouflon and aoudad sperm) and maintained at 5 °C for 1 h before adding glycerol (final concentration 5%). After a 15 min equilibration period in the presence of glycerol, the samples were frozen. For the ibex, there was enhanced (P < 0.05) sperm viability and acrosome integrity after the 3 h as compared with the 15 min equilibration time. For the chamois, subjective sperm motility and cell membrane functional integrity were less (P < 0.05) following 15 min of equilibration. In the mouflon, progressive sperm motility and acrosome integrity was less (P < 0.05) when the equilibration time was reduced to 15 min. For the aoudad, the majority of sperm variables measured were more desirable after the 3 h equilibration time. The freezing-thawing processes reduced the sperm head size in all the species studied; however, the equilibration time further affected the frozen-thawed sperm head variables in a species-dependent fashion. While the equilibration time for chamois sperm might be shortened, this appears not to be the case for all ungulates.