Diluents for Bovine Semen. XII. Fertility and Motility of Spermatozoa in Skimmilk with Various Levels of Glycerol and Methods of Glycerolization

Abstract

Laboratory studies showed that the beneficial effect of glycerol on the maintenance of sperm motility in skimmilk diluent during 5 C storage was related both to level and method of glycerol addition. Optimum livability was obtained with 5% glycerol and when the glycerol-containing fraction was added stepwise to the partially diluted semen at 5 C. Direct addition of semen to completely formulated skimmilk-13% glycerol diluent at room temperature significantly reduced sperm livability as compared to that in partially diluted semen glycerolated in a stepwise fashion at 5 C. Even when glycerol level in the complete diluent was lowered from 13 to 5%, and the semen added at room temperature, livability during 14 days of storage was slightly better in the skimmilk-13% glycerol control samples glycerolated stepwise at 5 C. Dilution at room temperature into completely formulated skimmilk-glycerol diluents containing more than 5% glycerol also resulted in abnormal sperm motility (circular or backward movement). In skimmilk-glycerol diluents containing 5, 10, and 20% glycerol, livability was superior (P < 0.01) when the glycerol fraction was added to the partially diluted semen at 5 C in three steps rather than all at once at 5 C or dropwise during the cooling process. Irrespective of glycerolization method, there was a highly significant increase in mean livability with each decrease in glycerol level. However, based on a split-sample field trial involving 9,606 first inseminations, fertility on any of the four days of use was not significantly different in skimmilk-diluted semen containing 5% rather than 10% glycerol. © 1962, American Dairy Science Association. All rights reserved.