Abstract: [Objective] To investigate the effects of castration on serum antioxidant indexes in male dogs. [Method] A total of 12 healthy male Chinese rural dogs aged around one year were randomly assigned into a control group or a castration group with 6 dogs per group. The formal experiment was performed after a 5-day pre-feeding period. At the initial of the experiment, blood samples of the experimental dogs were collected. The testectomy was performed in the dogs in castration group, and the dogs in control group received no testectomy. The blood samples of the experimental dogs were collected on 5^th, 10^th and 15^th days after testectomy, and the serums were obtained by centrifugation. The activities of superoxide dismutase （SOD） and glutathione peroxidase （GSH-Px） as well as the contents of hydrogen peroxide （H₂O₂） and malonaldehyde （MDA） in serums of the dogs in castration group and control group were determined and statistically compared. [Result] No significant （P>0.05） differences in serum SOD activities between control group and castration group were observed. On 5^th, 10^th and 15^th days after testectomy, the serum GSH-Px activities of castration group were significantly （P<0.05） lower than those of control group. Castration group had extremely significantly （P<0.01） higher serum contents of MDA and H₂O₂ on 10^th and 15^th days after testectomy compared with control group. [Conclusion] Castration has no significant effect on the serum SOD activities of male dogs, but significantly reduces the serum GSH-Px activities and elevates the serum contents of MDA and H₂O₂.

Key words: male dogs, castration, hydrogen peroxide, superoxide dismutase, glutathione peroxidase, malonaldehyde