Effect of Heterospermic Insemination on Fertility of Cattle

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Abstract
In 1971, 1972 and 1973 cattle were inseminated with frozen semen from three individual bulls (homospermic) and seminal mixtures from these bulls (heterospermic). Post-thaw spermatozoan motility in heterospermic treatments was not superior to homospermic treatments. The number of motile spermatozoa after thawing ranged from 7.4 to 12.1 × 106 per inseminate but less than 2% of the variability in first-service pregnancy rate was due to spermatozoal numbers. No signiFicant increase in fertility was obtained when insemination with mixtures of semen from two bulls was compared to homospermic insemination. The first-service pregnancy rate of 70.6% for 323 services with the seminal mixtures from three bulls was significantly higher (P < .05) than the 62.7% for 327 homospermic inseminations or 62.2% for 323 services with the seminal mixtures from two bulls. The overall mean pregnancy rate (first and second services combined) for the triple-seminal mixtures was higher than the single and double-seminal mixtures for each group of cattle inseminated. Heterospermic inseminations with frozen semen resulted in a deviation from the expected equal number of progeny per sire. Copyright © 1975. American Society of Animal Science . Copyright 1975 by American Society of Animal Science.

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