Fertility of Bovine Spermatozoa Stored at Minus 79° C. for One Week and for Seventeen Weeks

Abstract

In a split-ejaculate experiment involving 75 ejaculates from 8 Holstein sires during two 3-month experimental periods, the 60- to 90-day percentage nonreturns was 71.0 for 1278 first services to unfrozen semen, 73.2 for 1151 first services to frozen semen stored 1 week at -79[degree] C, and 69.8 for 1094 first services to frozen semen stored 17 weeks at -79[degree] C. These differences, which were not significant even at the 10% level of probability, confirm the previous results with frozen semen reported from this laboratory. The average spermatozoan survival rate for all ejaculates was 77% after 1 week storage and 62% after 17 weeks storage at -79[degree] C. The estimated number of motile spermatozpa per milliliter of extended semen at the time of breeding was 8.6 x 106, 11.6 x106, and9.3 x 106 for the unfrozen, 1-week frozen, and 17-week frozen semen, respectively. Within treatments, there were no significant and useful correlations between the number of spermatozoa inseminated and fertility. A frozen semen kit capable of maintaining a temperature of approximately -79[degree] C for 6 days with a loss of 2 lb. of dry ice per day is described.