EVALUATION OF MEMBRANE INTEGRITY OF CRYOPRESERVED BOVINE SPERM TO PREDICT PREGANANCY RATES

Abstract

Semen of twelve Tabapuã young bulls, which were according to patterns established by CBRA (1998) after cryopreservation, was submitted to fast and slow thermoresistence tests, hypoosmotic swelling test, induced acrosome reaction by heparin, sperm viability test by Trypan blue post-freezing and post-incubation with heparin, and pregnancy rates at first artificial insemination of Nellore heifers. Continuous variable averages of the mentioned tests were compared by Student–Newman–Keuls test and subjective variables were compared by Kruskal-Wallis non-parametric test (p<0.05). Simple correlation among all variables, and multiple regression models to predict pregnancy rate of Nellore heifers, using semen of Tabapuã bulls, were estimated. It was shown that none of the variables studied to evaluate membrane integrity in frozen semen was isolately effective (p>0.05) to preview pregnancy rate, even if using the multiple regression model that included all variables. One can conclude that the model proposed in this study was not effective to predict pregnancy rate. Hypoosmotic Swelling Test can be suggested to evaluate functional and structural integrities of plasma membrane and the capacity of spermatozoa going through acrosome reaction.
KEYWORDS: hypoosmotic swelling test; induced acrosome reaction; semen; sperm membrane; thermoresistence test.