Motility and Fertility of Bull Semen Extended at High Rates in Yolk Extender Containing Catalase

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Abstract
Sperm survival in 20% yolk extender (CUE and CU-16) during a 12-day storage period was improved by catalase. The improvement was greater for semen extended to five million motile sperm per milliliter than for semen extended to ten million (P<.01), thus reducing the dilution effect on motility. However, fertility tests of semen used for insemination within a few days of collection showed no beneficial effect of catalase on fertility. In two trials the control CUE extender averaged 71.0 and 76.9% 60- to 90-day nonreturns compared with 71.5 and 74.6% non-returns for CUE containing 20 jig of catalase per milliliter. When bull semen was extended to five million motile sperm vs. ten million motile sperm per milliliter of CUE extender, no difference in fertility was observed (P<.05). In two trials totaling 64,930 inseminations, the 60- to 90-day percentage of nonreturns for 5 x 106 motile sperm were 74.6 and 75.2, and for the control 10 x 106 motile sperm were 76.1 and 76.1. These results clearly indicate that the usefulness of genetically superior sires can be increased by reducing the number of sperm per insemination.