The aim of this study was to compare the effectiveness of antioxidants including cysteamine (2.5, 7.5 mM), hyaluronan (0.25, 1 mg ml 1) and fetuin (5,10 mg ml 1) in the freezing of Brown Swiss bull semen. The best percentagesof CASA motilities were achieved with 10 mg ml 1 of fetuin and 2.5 mM of cysteamine. For sperm morphology, 10 mg ml 1 of fetuin and 2.5 mM of cysteamine had better protective effects (P < 0.001). The results of hypo-osmotic swelling test showed that the percentage values of membrane integrity in all the groups, excluding that supplemented with 5 mg ml 1 of fetuin, were higher than those of the control group (P < 0.001). Results obtained for the
DNA damage of sperm cells demonstrated that 0.25 mg ml 1 of hyaluronan, and 2.5 and 7.5 mM of cysteamine led to lower rates of spermatozoa with damaged DNA, compared with the control group (P < 0.001). The maintenance of superoxide dismutase and glutathione peroxidase antioxidant activities following freeze-thawing with 2.5 and 7.5 mM of cysteamine and 10 mg ml 1 of fetuin was demonstrated to be at a higher level in comparison with the control group (P < 0.001). Malondialdehyde formation was found to be lower in the groups supplemented with 0.25 mg ml 1 of hyaluronan and 7.5 mM of cysteamine after the freeze-thawing process (P < 0.001).