Abstract: [Objective] This study aimed to investigate the therapeutic effect of Salvia miltiorrhiza polysaccharide on dairy cow subclinical mastitis,so as to provide a novel natural medication regimen for its clinical prevention and treatment.[Method] A total of 60 dairy cows clinically diagnosed with subclinical mastitis were randomly allocated into the control group（CG）,low-dose Salvia miltiorrhiza polysaccharide group（LG）,medium-dose group（MG）and high-dose group（HG）,with 15 individuals per group.The cows received 7-day consecutive intramammary infusion treatments of normal-saline,5,10 and 15 mg/kg·bw Salvia miltiorrhiza polysaccharide,respectively.The therapeutic efficacy of Salvia miltiorrhiza polysaccharide was assessed by detecting milk somatic cell count（SCC）,milk composition parameters and serum inflammatory factor levels before and after treatment.[Results] The therapeutic effect of Salvia miltiorrhiza polysaccharide on dairy cow subclinical mastitis exhibited dose-dependence.On Day 7 post-treatment,the milk SCC of HG decreased extremely significantly in contrast to the control group（P＜0.01）,falling from（286.42±35.17）×10⁴ cells/mL at baseline to（82.15±12.34）×10⁴ cells/mL.Milk protein and lactose contents in MG and HG were significantly higher than those in CG（P＜0.05）,while no obvious difference was observed for milk fat percentage.Compared with the control group,serum tumour necrosis factor-α (TNF-α) and interleukin-6（IL-6）concentrations were markedly reduced,and interleukin-10（IL-10）content was significantly elevated in the polysaccharide-treated groups（P＜0.05）.Moreover,the average daily milk yield of HG dairy cows rose by 12.6 % on the 7th treatment day relative to CG,presenting statistically significant difference（P＜0.05）.[Conclusion] Intramammary infusion with 15 mg/kg·bw Salvia miltiorrhiza polysaccharide can effectively lower milk SCC,regulate systemic inflammatory responses,ameliorate milk quality and improve milk yield.Accordingly,it delivers favourable curative effects against subclinical mastitis in dairy cows.

Key words: salvia miltiorrhiza polysaccharide, dairy cow, subclinical mastitis, therapeutic effect