Influence of glycerol levels, diluent and post-thaw temperature on motility and acrosomal maintenance in bovine semen frozen in plastic straws.

One ejaculate from each Of 13 bulls was used to determine the influence of glycerol level on post-thaw susceptibili ty of spermatozoa in French straws to cold shock. Treatments were arranged factorially and included yolk-Tris and yolk-citrate diluents; 7, 9 and 11% glycerol ;and exposure to 1, 20 or 37 C water baths for 3 rain immediately post-thaw. Percentage of motile spermatozoa and percentage of intact acrosomes were quanti tated after 0-, 4and 8-hr incubation at 37 C to determine the effect of the post-thaw treatments on spermatozoa. Within each diluent and glycerol level, significant (P<.01) damage to cells resulted from the 1 C post-thaw treatment. Percentage of glycerol in the yolk-citrate diluent did not affect acrosomal maintenance in any of the post-thaw treatments. However, in the yolk-Tris diluent, 11% glycerol significantly (P<.01) reduced the percentage of intact acrosomes in all postthaw treatments. Within the 7 and 9% glycerol levels Tris buffered semen had higher (P<.01) percentage of motile spermatozoa than the citrate buffered semen when both were exposed to the 20 C and 37 C post-thaw treatments. (