RELATIONSHIP BETWEEN SPERM ZONA-PELLUCIDA BINDING ASSAYS AND THE 56-DAY NONRETURN RATE OF CATTLE INSEMINATED WITH FROZEN-THAWED BULL SEMEN

Assays based on sperm-zona pellucida binding have been developed as di agnostic tests to predict the fertilizing potential of mammalian sperm atozoa. Recently, we reported on the development of a sperm-zona pellu cida binding assay (SZBA) for bull spermatozoa. The aim of the present study was to develop a hemi-zona assay (HZA) for bull spermatozoa and to investigate the relationship between SZBA and HZA outcomes and in vivo fertility. Frozen-thawed semen samples from 8 fertile Swedish Red and White bulls (one ejaculate per bull) designated as the test semen samples and a single ejaculate from a fertile Holstein-Friesian bull designated as the control semen sample were used in this study. In the SZBA, 2 groups of 20 oocytes per semen test sample and in the HZA a m inimum of 6 matching pairs of hemi-zonae were used for comparison of s perm binding with control semen. Sperm binding to matching hemi-zonae of individual semen samples was equal, and clearly demonstrated the fe asibility of the HZA for cattle. A significant correlation was found b etween the SZBA and the HZA indices obtained from the different semen test samples (r=0.42, P<0.001; n=67). There was no significant relatio n between the SZBA indices and the 56-d nonreturn rate of the test sam ples. However, the HZA indices of the semen test samples and the 56-d nonreturn rate were significantly correlated (r=0.46, P<0.0001; n=67). It is concluded that HZA can be regarded as a potential assay for pre dicting the fertilizing ability of bovine semen samples. However, furt her studies using more semen samples are necessary to confirm this vie w. (C) 1997 by Elsevier Science Inc.