Effect of Method of Glycerol Addition on the Fertility of Frozen Bovine Spermatozoa

An experiment was conducted to determine the optimum method of adding glycerol to bovine spermatozoa for freezing. Two separate semen collections were taken from six different bulls. A total of 3,005 first-service cows were bred. Each semen collection was used on a split-sample basis. Four methods of glycerolization were employed; namely, (A) addition of the glycerolated buffer to the nonglycerolated semen portion at 5 C., (B) at 10 C., (C) at 20 C., and (D) addition of freshly collected semen directly to the total glycerolated buffer. Respectively, a total of 770, 742, 723, and 770 first-service cows were bred. The nonreturn rates based on 75-day nonreturns were 65.1% when the glycerol portion was added at 5 C., 65.4% when added at 10 C., 62.7% when added at 20 C., and 64.0% when the semen was added directly to the total volume of glycerolated buffer.