The Effect of Glycerol Level and Rate of Freezing, for Various Extenders, on the Survival of Bovine Spermatozoa Frozen and Stored at −79° C

Erickson et al. (5) used a cooling rate of 3 ° C. per minute, and O'Dell and Ahnquist (9) used slower rates of cooling.Williams (.17) reported his best freezing rate as I ° C. per minute down to -15 ° C. and then at a faster rate to -79 ° C.Although different combinations of glycerol lew, ls and rates of freezing for different extenders have been compared by l)mm and llafs (3) and by Erickson et al. (5), the optimum combinations of these variables have not been definitelyestablished.The experiment reported here was initiated to determine the optimum levels of glycerol and rates of freezing' for three extenders.EXI'ERIMlgNTA L I~RO('EI)URE Semen used in this experiment was t, ollected from a Holstein bull once weekly for a period of time snffieient to obtain 10 usable collections.First and second ejac, ulates were pooled in order to have a sufficient quantity of semen.