EPIDIDYMAL COMPOUNDS AND ANTIOXIDANTS IN DILUENTS FOR THE FROZEN STORAGE OF RAM SPERMATOZOA

The epididymal compounds taurine, hypotaurine and inositol, and the an tioxidants carnosine and ascorbic acid, were added to Tris-based dilue nts containing varying concentrations of glycerol, and their effect on the post-thaw motility characteristics and fertility of ram spermatoz oa was examined. Overall, the post-thaw motility characteristics of sp ermatozoa were better when semen was frozen in the presence rather tha n in the absence of glycerol. Only taurine protected spermatozoa durin g cryopreservation; the presence of 25 mM or 50 mM taurine significant ly improved the post-thaw percentage of motile spermatozoa but this ha d no effect on fertility after cervical or laparoscopic insemination o f ewes. Increasing the concentration of taurine to more than 100 mM si gnificantly reduced the percentage of motile spermatozoa, compared wit h the lower concentrations of the amino acid. The presence of more tha n 50 mM carnosine or ascorbic acid significantly reduced all motility characteristics compared with the control diluent. Given that hypotaur ine, carnosine, or ascorbic acid did not improve post-thaw motility, t he cryoprotective effect of taurine may be attributable to its osmoreg ulation rather than to its antioxidant properties.