Fertility of Bull Semen Stored Up to Four Days at 5° C. In 20% Egg Yolk Extenders

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Abstract
Three fertility trials comparing extenders CU-16 and CUE with a 50% yolk-citrate control were conducted using 10 million motile sperm per ml of extended semen. The 1st trial included 4 bulls, and the semen was used for insemination primarily 1 and 2 days after collection. A 2d field trial was designed to use semen extended with CUE and CU-16 more extensively 3 to 4 days after collection, and a 3d field trial, conducted on a larger scale, was designed to obtain results with all 3 extenders over a 4-day storage period. The combined number of 1st services and weighted mean percentages of 60- to 90-day nonreturns for all 3 trials was 6069 and 73.4 for the control 2.9 CSAY, 6280 and 76.6 for the CUE, and 6145 and 76.0 for the CU-16. The adoption of CUE for routine use by the local artificial breeding cooperative resulted in an immediate and consistent increase of about two percentage units, bringing the 60- to 90-day nonreturn rate to an average of 74.9% for nearly 300,000 first inseminations.