Effect of rapid warming of bull and rabbit semen.

Rapid warming of semen from 5 to 37 degrees C caused visible damage to the acrosomes of bull and rabbit spermatozoa. The degree and type of damage varied with the species, the bull being the more resistant. While vesiculation was observed in rabbit spermatozoa, neither warm nor cold shock resulted in this defect in the bull. Warm shock of bull spermatozoa caused acrosomal knobbing in an anterior region of the head. Spermatozoa with thread and/or droplet-like structures were frequently observed in bull semen after cold shock.