Effect of Cooling, Storage, Glycerolization and Spermatozoal Numbers on Equine Fertility1

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Abstract
The effects of cooling, storage, glycerolization and spermatozoal numbers on fertility were investigated utilizing three stallions and 72 mares. Semen was extended in a cream-gel extender and inseminated: a) within 1 hr (fresh) at 38 C, b) after cooling for 2 hr to 5 C, c) after cooling for 2 hr plus the addition of 7% (v/v) glycerol, and d) after cooling for 24 hours. One-half of the mares were inseminated with 100 and one-half with 500 × 106 progressively motile spermatozoa per insemination. First-cycle pregnancy rates of 55.6, 38.9, 5.6 and 27.8% were obtained with the fresh, cooled 2 hr, cooled 2 hr plus glycerol and the cooled 24-hr seminal treatments, respectively; after three cycles, the pregnancy rates were 94.4, 83.3, 44.4 and 55.6%. The fertility of freshly extended semen was superior (P<.05) to that of semen cooled for 2 hr plus glycerol and to semen cooled and stored for 24 hours. Semen cooled for 2 hr was superior (P<.05) to semen cooled for 2 hr plus glycerol. The 63.9% pregnancy rate for mares inseminated with 100 × 106 did not differ (P>.05) from the 75.0% for mares receiving 500 × 106 spermatozoa. There was no difference in fertility among the three stallions. Copyright © 1976. American Society of Animal Science . Copyright 1976 by American Society of Animal Science