Frozen boar spermatozoa: methods of thawing pellets.

In four experiments, the effects of pre-thaw delay, method of thawing, temperature of thawing solution and pellet volume on acrosome morphology and moti l i ty of" boar spermatozoa frozen by the pellet method were examined. Holding the frozen pellets for 0, 1.5, 3 or 4.5 min in a Styrofoam container before transferring them into the thawing solution resulted in maximum post-thaw percentages of normal apical ridge (NAR) acrosomes and motile spermatozoa at 3 minutes. Thawing frozen pellets in solutions resulted in higher post-thaw percentages of NAR acrosomes than thawing in a Teflon-coated pan (P<.005); however, the opposite result was obtained for percentage of motile spermatozoa. Thawing frozen pellets in a solution heated to 50 C resulted in higher percentages of NAR acrosomes and motile spermatozoa than thawing in a solution heated to 40 or 60 C. Pellet volumes of .09, .18 or .27 ml had no effect on the percentage of NAR acrosomes after thawing; however, there was a significant positive linear relationship between pellet volume and motil i ty (P<.005). (