Astragalus root extract improved average daily gain, immunity, antioxidant status and ruminal microbiota of early weaned yak calves

BACKGROUND Early weaning in yak calves is being attempted to improve yak reproduction rate. However, this has to be done with caution because of the high mortality rate of calves due to the lack of nutrients and the harsh environmental conditions. Twenty-four weaned male yak calves were used in a 60 day feeding trial in which astragalus root extract (ARE) was supplemented. They were assigned randomly to one of four dietary treatments (n= six per treatment) that differed in ARE level: 0 g kg(-1)(control), ARE(0); 20 g kg(-1), ARE(20); 50 g kg(-1), ARE(50;)and 80 g kg(-1)dry matter intake (DMI), ARE(80). RESULTS Final bodyweight and average daily gain (ADG) were significantly higher and the DMI/ADG ratio was significantly lower in calves with ARE supplementation than control (ARE(0)) calves. Ruminal concentrations of acetate and propionate and serum concentration of superoxide dismutase in ARE(80)calves were higher than in the other groups and serum concentration of insulin was higher in ARE(80)calves than in ARE(20)calves. Serum immunoglobulin G (IgG) and interleukin-2 (IL-2) concentrations in ARE-fed calves were higher than in controls. Serum tumor necrosis factor (TNF-alpha) concentration was higher in ARE(50)and ARE(80)groups than ARE(0)calves and serum interleukin-6 (IL-6) concentration was higher in ARE(80)than in ARE(0)calves. Serum immunoglobulin A (IgA), IgG and immunoglobulin M (IgM) concentrations increased with age in ARE-fed calves. ARE supplementation increased the abundance of fiber degrading bacteria. CONCLUSION ARE at a dosage of 5% to 8% DMI can be supplemented to early weaned yak calves to improve growth performance, antioxidant capacity and immunity. (c) 2020 Society of Chemical Industry

Automated summary

The study showed that supplementing astragalus root extract (ARE) can significantly improve bodyweight and average daily gain in early weaned yak calves, lower the ratio of dry matter intake to average daily gain, enhance antioxidant capacity and immunity, and increase the abundance of fiber degrading bacteria.