Liquid storage of ram semen in the absence or presence of some antioxidants.

The antioxidants superoxide dismutase (SOD), catalase (CAT), cytochrome c (CHc) and glutathione peroxidase (GP) were added at various concentrations to Tris-glucose-yolk diluent (TGY), and their effects on motility, acrosome integrity and fertility of ram spermatozoa were assessed after extension and liquid storage. All the antioxidants improved the motility and acrosome integrity of spermatozoa, and a combination of SOD and CAT had an additive effect on the survival of spermatozoa stored at 5 degrees C but not at 25 degrees C. There was a linear improvement in survival of spermatozoa with increasing dose of antioxidants except for CAT for which doses higher than 200 U mL-1 were toxic. The proportion of oocytes fertilized in vitro declined with time of semen storage (P < 0.001), and was better for semen diluted with TGY containing SOD or CAT than TGY without antioxidants when stored for 7 days (116/246, 47% v. 25/79, 32%; P < 0.05) but not for 14 days (23/174, 13% v. 8/66, 12%). Fertilization rates were unaffected by the presence or absence in the diluent of CHc or GP. The proportions of ewes with fertilized ova and of recovered ova fertilized were better after insemination with semen diluted in TGY containing SOD and CAT than TGY without antioxidants when stored for 14 days (9/18, 50% and 20/40, 50% v. 2/13, 15% and 5/32, 16%; P < 0.05) but not for 7 days (9/20, 45% and 16/48, 33% v. 8/16, 50% and 24/41, 59%). Pregnancy rates were better after intrauterine insemination of ewes with fresh semen than stored semen (11/18, 61% v. 21/75, 28%; P < 0.01), and with semen stored in TGY containing SOD and CAT than in TGY without antioxidants (15/37, 41% v. 6/38, 16%; P < 0.05).