Astragalus membranaceus root supplementation improves average daily gain, rumen TVFA production and immunity and antioxidant factors of Tibetan sheep

Background: The use of antibiotics as supplements in animal feed is restricted due to possible health hazards associated with them. Consequently, there is increasing interest in exploiting natural products as antibiotics with no detrimental side effects. In this study, we examined the effect of Astragalus membranaceus root (AMT) supplementation on dry matter intake, growth performance, rumen fermentation and immunity of Tibetan sheep. Materials and methods: Twenty-four male Tibetan sheep (31 ± 1.4 kg; 9 months old) were assigned randomly to one of four dietary treatments with different levels of AMT: 0 g/kg, 20 g/kg, 50 g/kg and 80 g/kg dry matter (A 0 , A 2 , A 5 and A 8 , respectively) in addition to their basal diets. A 0 acted as a control group and measurements were recorded over a 56-d feeding period. Results: Sheep fed with AMT had a higher average daily gain (ADG) and a lower feed:gain ratio (F:G) than controls ( P < 0.001). Rumen concentrations of NH 3 -N ( P < 0.001), total volatile fatty acids (TVFA) ( P = 0.028), acetate ( P = 0.017) and propionate ( P = 0.031) in A 5 and A 8 were higher than in A 0 . The addition of AMT in the feed significantly increased serum antioxidant and immunity factors of the sheep and increased the concentrations of serum interleukin, immunoglobulin and tumour necrosis factor-α (TNF-α) ( P = 0.010). Conclusions: We concluded that AMT can be used as a feed additive to improve growth performance and rumen fermentation and enhance the immunity of Tibetan sheep. Some responses exhibited a dose-dependent response, whereas other did not exhibit a pattern, with an increase in AMT. The addition of 50 g/kg and 80 g/kg AMT of total DMI showed the most promising results.