FERTILITY OF RANGE BEEF BULLS GROUPED ACCORDING TO PRESENCE OR ABSENCE OF HEPARIN-BINDING PROTEINS IN SPERM MEMBRANES AND SEMINAL FLUID

Trials were performed to determine the relationship of heparin-binding proteins (HBP) to fertility of bulls. Red Angus (142), Santa Gertrudi s (59), Gelbvieh (59), and Santa Gertrudis x Gelbvieh (40) bulls were identified according to the presence or absence of the greatest affini ty HBP (HBP-B5) on sperm membranes and in seminal fluid. Nine to 20 bu lls with the same HBP-B5 profiles were assigned to pastures with Santa Gertrudis cows at a ratio of 1 bull:25 cows. Fertility for Group 1 (8 0 bulls with HBP-B5 in sperm membranes but undetectable HBP-B5 in semi nal fluid, in six pastures) was 82% pregnant of 1,692 cows. Group 2 bu lls (48 bulls with HBP-B5 detectable in seminal fluid and in sperm mem branes, in four pastures) impregnated 67% of 919 cows. Fertility for G roup 3 (37 bulls with HBP-B5 in seminal fluid but undetectable HBP-B5 in the sperm membranes, in three pastures) and Group 4 (56 bulls with undetectable HBP-B5 in seminal fluid and sperm, in four pastures) was 63% pregnant; of 747 and 1,208 cows, respectively. Group 1 had an aver age of 17% greater fertility compared with Groups 2, 3, and 4 (P <.05) . In conclusion, groups with the greatest affinity HBP-B5 in sperm: me mbranes but not in seminal fluid had greater fertility than did groups with other HBP-B5 profiles.