Influence of various antioxidants on microscopic-oxidative stress indicators and fertilizing ability of frozen-thawed bull semen

The aim of this study was to determine the effects of oxidized glutathione (GSSG), reduced glutathione (GSH) and bovine serum albumin (BSA) on standard semen indicators (motility, acrosome and total abnormalities, HOST), endogenous antioxidant enzyme activities and fertilizing ability of frozen-thawed bull semen. Eighteen ejaculates from each of 3 Holstein bulls were collected using an artificial vagina and 9 replicates of the ejaculates were diluted with a Bioxcell-based extender supplemented with antioxidants, including BSA (5 mg/mL), GSH (2 mM), GGSG (2 mM), and an extender containing no antioxidants (control). Insemination doses were prepared for the insemination of cows at observed oestrus. Supplementation with antioxidants led to lower percentages of acrosome damage (4.0+/-0.5%, 4.4+/-0.5%, 4.0+/-0.3%, respectively) and total abnormalities (10.3+/-0.7%, 9.7+/-0.8%, 10.4+/-0.6%), compared with the controls (6.5+/-0.6 and 14.9+/-1.1%, P less than 0.01). Pregnancy rate after insemination was highest (72.2%) in the group which was given BSA (P less than 0.05). There were no significant differences among groups in GSH and glutathione peroxidase enzyme activities. Superoxide dismutase activities (0.05+/-0.005, 0.03+/-0.005, 0.05+/-0.009 microkat/g protein, respectively) in all of the experimental groups with antioxidants were lower than the control group (0.11+/-0.024 microkat/g protein, P less than 0.001). Furthermore, BSA increased (P less than 0.001) the activity of catalase (304.23+/-114.69 microkat/g protein), following the freezing-thawing process.