Fertility of Bull Semen Frozen with β-Amylase, β-Glucuronidase, and Catalase

“Capacitase,” a product combining β-amylase and β-glucuronidase, was compatible with survival of bull spermatozoa frozen in whole milk-glycerol extender at final concentrations per ml of 0, 5, 10, and 20 μg of β-amylase combined with 0, 75, 150, and 300 units of β-glucuronidase, respectively. Bull semen was frozen in whole milk-glycerol extender containing the three lower concentrations of enzymes tested in the previous trial and used to inseminate 9057 first-service cows within 4 mo of freezing. The 60- to 90-day percent nonreturns were 74.6, 75.6, and 75.0. The same treatments plus a fourth one containing 10 μg of catalase per ml were fertility tested in another trial. Insemination of 16,842 cows resulted in 75.6, 74.1, 74.6, and 74.2% nonreturns. In this trial semen was held immersed in liquid nitrogen and distributed for immediate use each mo for 6 mo. There was no change in fertility during 6 mo of continuous storage at −196 C. Under the conditions tested neither catalase nor β-amylase with β-glucuronidase enhanced fertility of frozen bull semen.