The sperm chromatin structure assay. Relationship with alternate tests of semen quality and heterospermic performance of bulls.

Data obtained by the sperm chromatin structure assay (SCSA) on spermatozoa from nine bulls were correlated with fertility, measured by heterospermic performance (-0.94, P less than 0.01) and by alternate tests of sperm quality, including motility, acrosome integrity, Sephadex filtration and morphology of spermatozoa (all significant at P less than 0.05 to P less than 0.01). The SCSA uses flow cytometry to determine the susceptibility of nuclear DNA to low pH-induced denaturation in situ as measured by the ratio of acridine orange binding to double- or single-stranded DNA. The error associated with multiple SCSA measurements was relatively low. The primary finding is that the assay of chromatin structure stability performed on killed spermatozoa was as highly correlated with the heterospermic performance of semen as the best of the classical tests for semen quality. The SCSA may therefore be a highly useful technique for evaluation of sperm quality.