Correlation between post-thaw motility and acrosomal integrity of bovine sperm

The relationship between post-thaw motility and the percentage of sperm with intact acrosomes was evaluated in semen from 26 yearling Hereford or Angus bulls. A total of 409 samples was used, which consisted of 208 pooled first and second ejaculates, split and frozen in ampules and straws. All bulls passed a breeding soundness exam several weeks prior to the experiment. However, bulls were not subjected to any further selection for seminal quality, and all were of unknown fertility. In addition, all ejaculates from each bull were frozen without regard to seminal quality. Motility was assessed immediately after thawing, whereas acrosomal integrity was evaluated after 2 h of post-thaw incubation at 38 degrees C. The simple coefficient of correlation among bulls between motility and percentage of sperm with intact acrosomes was only .33. When variation in seminal quality among bulls was removed statistically, the corresponding coefficient of correlation within bulls was only .23. Under conditions of this experiment, post-thaw motility and acrosomal integrity constituted distinct, separate features of spermatozoal integrity that varied independently of each other.