Abstract:

【Objective】 The objectives of this study were to investigate the effects of nano-zinc supplementation in dietary on the semen quality parameters, the activities of antioxidant enzyme in seminal plasma and the expression of copper zinc superoxide dismutase in epididymis of ram lambs, and to analyze the correlation between semen quality parameters and the activities of antioxidant enzyme.【Method】Sixteen 9-month-old Jinzhong ram lambs with good health and approximate weight were randomly divided into 4 groups, fed with a basal diet with supplementation of 0, 50, 100 and 150 mg·kg^-1 DM nano-zinc, respectively. The experimental period was 90 d. Semen was collected on 78 d and 79 d in consecutive two days, samples of 100 µL fresh semen was used to analyze semen quality parameters, the rest of fresh semen sample was centrifuged at 2 000 r/min for 10 min, the supernatant (seminal plasma) was collected for measurement of the activities of copper zinc superoxide dismutase, glutathione peroxidase and total anti-oxidation competence. All rams were castrated for collection of epididymis caput, corpus and cauda at the end of experiment. Expression of Cu-ZnSOD protein in epididymis was detected and located by immunohistochemistry. The mean optical density was analyzed with Image Pro Plus 7.0 software.【Result】The results showed that there was no significant difference in ejaculate volume between the treatment groups and control group (P＞0.05). Compared with the control group, the groups with supplementation of 50 mg·kg^-1 or 100 mg·kg^-1 nano-zinc had higher sperm concentration, sperm motility and membrane integrity, and less percentage of abnormal sperm. The group with supplementation of 150 mg·kg^-1 had higher membrane integrity than control group, while it had no significant difference in sperm concentration, sperm motility with control group. The rams in groups with supplementation of 50 mg·kg^-1 or 100 mg·kg^-1 nano-zinc also had higher activities of Cu-ZnSOD, GPxs and total anti-oxidation competence, and less MDA concentration in seminal plasma. The rams in group with supplementation of 150 mg·kg^-1 had higher total anti-oxidation competence than the control group, while they had no significant difference in activities of Cu-ZnSOD, GPxs and MDA content with rams in the control group. The result of immunohistochemistry showed the positive signals were detected in pseudostratified columnar epithelium in epididymis caput and corpus, and simple columnar epithelium in epididymis cauda. The order of expression of Cu-ZnSOD protein in epididymis from rams in the treatment group was corpus＞caput＞cauda, while those in the control group was caput＞corpus＞cauda. The mean optical density of Cu-ZnSOD was higher in the group with supplementation of 50 mg·kg^-1 or 100 mg·kg^-1 nano-zinc in epididymis caput and corpus. The activity of Cu-ZnSOD in seminal plasma had a positive correlation with sperm concentration, sperm motility and membrane integrity, and a negative correlation with percentage of abnormal sperm.【Conclusion】The optimal supplementation of 50 mg·kg^-1 or 100 mg·kg^-1 nano-zinc in diet could improve semen quality and seminal plasma anti-oxidase activities, and the expression of Cu-ZnSOD in epididymis of rams. The activity of Cu-ZnSOD in seminal plasma could be regarded as index of evaluation of semen quality in sheep production. The further researchs need to be done in molecular mechanism of trace element zinc regulation on semen quality.

Key words: expression of Cu-ZnSOD, semen quality parameter, anti-oxidase in seminal plasma, epididymidis, ram