Abstract: [Objective] To investigate the effects of Astragalus polysaccharides on production performance, antioxidant capacity and immune function of dairy cows,and to provide theoretical basis for improving dairy cattle breeding efficiency and health management. [Method] Seventy-two cows with similar first litter,milk production and body condition were selected and randomly divided into four groups：control group （CON）,low-dose group （APS 1.5）,medium-dose group （APS 3.0） and high-dose group （APS 4.5）.The control group was fed the basal diet,and the other three groups were fed the basal diet supplemented with 1.5,3.0,and 4.5 g/kg Astragalus polysaccharide,respectively.The pre-experimental period lasted 15 d,and the formal experimental period lasted 60 d.during which milk production,milk composition,antioxidant indicators and immune indicators were monitored and analyzed. [Result] Milk production in the APS 3.0 group was significantly improved,milk protein rate,milk fat rate and dry matter content were improved,and somatic cell number was significantly reduced;serum total antioxidant capacity （T-AOC）,superoxide dismutase （SOD）,glutathione peroxidase （GSH-Px） activities were significantly increased,and malondialdehyde （MDA） content was significantly reduced in each experiment group;The immunoglobulin IgA and IgM contents in the astragalus polysaccharide-supplemented groups were significantly increased,while the tumor necrosis factor-α (TNF-α) content was significantly decreased,with the medium-dose group showing the optimal effect. [Conclusion] Astragalus polysaccharide cansignificantly improve the production performance of dairy cows,enhance antioxidant capacity and immune function,among which 3.0 g/kg addition has the best effect and has high application value in breeding.

Key words: Astragalus polysaccharide, production performance, antioxidant, immune function, dairy cattle