Fertility of frozen bovine spermatozoa packaged in continental straws or ampules.

Fertility of semen frozen in .25-ml Continental straws or 1.0-ml ampules was compared in two field trials. Semen from four bulls was used to inseminate 574 cows over 38 days in Trial 1. Rates of pregnancy for cows inseminated with semen in straws or ampules were 54 and 32% for first-service inseminations and 70 and 50% at the end of the breeding period. Semen from one bull was used to inseminate 204 cows over 44 days in Trial 2. Rates of pregnancy from single inseminations averaged 58 and 44%, while corresponding values at the end of the breeding period were 83 and 67% for semen in straws and ampules.