Viability and fertility of stallion semen frozen with ethylene glycol and acetamide as a cryogenic agent

This study was designed to determine the effect of cooling at a rate of -0.13 degrees C/min or any slow cooling prior to freezing on stallion sperm and to determine the effect of two thawing temperatures on the viability of sperm frozen using a lactose-EDTA-egg yolk extender (LAC) with 3.5% ethylene glycol (LAC 3.5% EG) or a LAC with the additional incorporation of methyl cellulose, trehalose and acetamide (LAC+5% AC). No differences were observed in the post-thaw parameters of sperm frozen using either one of the cryogenic agents or frozen with or without previous slow cooling. Thawing at 75 degrees C was better than at 37 degrees C (P < 0.05). An interaction was observed between the cryoprotectant and the freezing protocol (P < 0.05). A conception rate of 23.3% was obtained after AI using equine semen frozen with LAC+5% AC.