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Factors Affecting the Fertility of Frozen Bovine Spermatozoa¹

Department of Dairy Husbandry, University of Minnesota, St. Paul

ABSTRACT

Three separate studies were conducted in an attempt to determine the most suitable extender, the spermatozoan concentration necessary, and the method of filling and sealing glass ampules, to obtain optimal nonreturn rates with frozen bovine spermatozoa.

In the first experiment, a total of 934 first-service cows were bred with semen extended and frozen in yolk-citrate extender, 945 cows with milk, 928 cows with yolk-glucose-glycine, and 902 cows with skimmilk. The 75-day nonreturn rates were 64.7, 66.2, 41.3, and 65.3%, respectively. Yolk-citrate, milk, and skimmilk, on the basis of this experiment, were acceptable semen extenders for frozen semen, whereas yolk-glucose-glycine was not suitable.

For the second experiment, 469 first-service cows were bred with frozen semen containing 10 million live spermatoza per insemination at time of initial dilution, 479 cows with frozen semen containing 20 million spermatozoa, and 472 cows with semen containing 30 million spermatozoa per insemination. The 75-day nonreturn rates for the respective levels were 63.1, 68.9, and 72.7%. The difference between the 10- and 30- million level was highly significant (P<0.01). The other differences were not significant.

In the third experiment, 294 first-service cows were inseminated with frozen semen for which the glass ampule had been gravity-filled-tip-sealed, 275 cows inseminated with frozen semen in ampules that had been gravity-filled-cut, pull-sealed; 313 cows inseminated with frozen semen in ampules that had been forced-filled-tip-sealed, and 254 cows inseminated with frozen semen in ampules that had been force-filled-cut, pull-sealed. The 75-day nonreturn rates for the respective methods of filling and sealing were 69.0, 73.8, 63.9, and 70.5%. None of the differences was significant. However, a significant difference existed between tip-sealed and pull-sealed, irrespective of method of filling. The difference between gravity-filled and force-filled, irrespective of method of sealing, was not significant.

¹ Paper No. 4034, Scientific Journal Series, Minnesota Agricultural Experiment Station.

² Present address: Tri-State Breeders' Cooperative, Westby, Wisconsin.