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

Wei, Haiyan; Ding, Luming; Wang, Xianju; Yan, Qi; Jiang, Cuixia; Hu, Changsheng; Wang, Guowen; Zhou, Yuqing; Henkin, Zalmen; Degen, Abraham Allan

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 d feeding trial in which astragalus root extract (ARE) was supplemented. They were assigned randomly to one of four dietary treatments (n = 6 per treatment) that differed in ARE level: 0 g kg-1 (control), ARE0 ; 20 g kg-1 , ARE20 ; 50 g kg-1 , ARE50; and 80 g kg-1 DMI, ARE80 . RESULTS Final bodyweight and average daily gain (ADG) were significantly higher and the DMI:ADG ratio significantly lower in calves with ARE supplementation than control (ARE0 ) calves. Ruminal concentrations of acetate and propionate and serum concentration of superoxide dismutase in ARE80 calves were higher than in the other groups and serum concentration of insulin was higher in ARE80 calves than in ARE20 calves. Serum IgG and IL-2 concentrations in ARE-fed calves were higher than in controls. Serum TNF-α concentration was higher in ARE50 and ARE80 groups than ARE0 calves and serum IL-6 concentration was higher in ARE80 than in ARE0 calves. Serum IgA, IgG and IgM concentrations increased with age in ARE-fed calves. ARE supplementation increased the abundance of fiber degrading bacteria. CONCLUSION Astragalus root extract at a dosage of 5% to 8% DMI can be supplemented to early weaned yak calves to improve growth performance, antioxidant capacity and immunity. This article is protected by copyright. All rights reserved.