Sperm in poor quality semen from bulls during heat stress have a lower affinity for binding hydrogen-3 heparin

Binding assays with [3H] heparin were performed using spermatozoa collected prior to, during, and following summer heat stress to dairy bulls. Ejaculates collected in August 1983 after a period of ambient temperatures exceeding 29.4 degrees C exhibited a high frequency of abnormal sperm, and motility was reduced in some samples. Sperm in samples collected during heat stress possessed dissociation constants for binding [3H] heparin ranging from 134.5 to 163.2 nmol. In contrast, sperm in semen collected prior to and after heat stress had significantly lower dissociation constants (higher affinity) for [3H] heparin, 12.9 to 56.4 nmol. The number of binding sites for [3H] heparin on sperm did not change among collection periods. It was concluded that the binding affinity for [3H] heparin may reflect membrane integrity of bull sperm.