Relationship of nonreturn rates of dairy bulls to binding affinity of heparin to sperm.

The binding of the glycosaminoglycan [3H] heparin to bull spermatozoa was compared with nonreturn rates of dairy bulls. Semen samples from five bulls above and five below an average 71% nonreturn rate were used. Samples consisted of first and second ejaculates on a single day collected 1 d/wk for up to 5 consecutive wk. Saturation binding assays using [3H] heparin were performed to quantitate the binding characteristics of each sample. Scatchard plot analyses indicated a significant difference in the binding affinity for [3H] heparin between bulls of high and low fertility. Dissociation constants were 69.0 and 119.3 pmol for bulls of high and low fertility, respectively. In contrast, the number of binding sites for [3H] heparin did not differ significantly among bulls. Differences in binding affinity of [3H] heparin to bull sperm might be used to predict relative fertility of dairy bulls.