Effect of Salvia miltiorrhiza polysaccharides on boar spermatozoa during freezing–thawing

Salvia miltiorrhiza polysaccharides (SMPs) were extracted from S. miltiorrhiza in this study. The aim of the present study was to evaluate the effect of SMP on the motility of boar sperm, including the antioxidant effect of SMP on boar sperm and the effect of SMP on the in vivo fertilizing ability of frozen–thawed boar sperm. Fifty ejaculates from 5 Swagger boars were collected and diluted with an extender, which contained 3% glycerol (v/v) with five concentrations of SMP (0.2, 0.4, 0.6, 0.8, and 1.0 mg/mL). The semen was frozen in 0.25 mL straws at 1.0 × 109 cells/mL. Sixty gilts were inseminated using fresh semen, frozen semen with 0.4 mg/mL of SMP and frozen semen without SMP. The results indicate that the addition of SMP to the extender results in a higher percentage of motile sperm post-thaw (P < 0.05). The activities of superoxide dismutase, lactate dehydrogenase, glutamic–oxalacetic transaminease and catalase were all determined to be significantly higher than the control group after adding SMP to the extender (P < 0.05). The artificial insemination (AI) results demonstrated that the litter size was significantly higher in the 0.4 mg/mL of SMP group than in the control group (P < 0.05). In conclusion, during the process of freezing, SMP can protect boar sperm from peroxidative damage and increase sperm motility and litter size during the process of freezing–thawing. The optimal concentration of SMP for the frozen extenders in this study was determined to be 0.4 mg/mL.