Monoclonal antibody detection of heparin-binding proteins on sperm corresponds to increased fertility of bulls.

A monoclonal antibody (M1) was produced against seminal fluid heparin-binding proteins (HBP) from a vasectomized bull. In the first part of this study, the presence of HBP in sperm or seminal fluid was determined for 53 bulls with an ELISA using M1. Bulls (8 to 18 per pasture) were bred to 1,114 cows at ratios of 1 bull:25 cows. Bulls with detectable HBP on sperm membranes were 11 percentage points more fertile than bulls with undetectable HBP in sperm membranes. In the second part of this study, three sperm, membrane HBP approximately 30, 24, and 21.5 kDa were identified with Western blots using M1. Santa Gertrudis bulls (n = 64) were bred to 1,354 Santa Gertrudis cows in groups with 2 to 11 bulls. Bulls with those three HBP (Group A) or a single 30-kDa HBP (Group B) in sperm membranes had the greatest fertility, ranging from 74.4 to 89.9% (mean = 81.5%) of the palpated cows that were pregnant. Bulls with the 21.5- and 30-kDa HBP (i.e., the 24-kDa HBP was absent; Group C) had a reduced fertility of 61.3%. Bulls without detectable HBP (Group D) resulted in 41.9% of 186 cows palpated pregnant. Bulls in Groups A and B were more (P < .01) fertile than all other groups. In conclusion, the presence of HBP in sperm membranes was indicative of the fertility potential of bulls.