The Effect Of Supplementing Astragalus Membranaceus On Growing Performance,Physiological Metabolism And Meat Quality Of Tibetan Sheep

With the development of intensive husbandry,quantity of antibiotics and other veterinary drug are used to improve animal production and reduce illness,which caused series of problems,such as antibiotics residues,hazards of animal products,etc.It is urgent to explore natural products to replace antibiotics in modern livestock feeding.In present study,we examined the effect of Astragalus membranaceus root supplementation on growth performance,meat quality,rumen fermentation,antioxidant properties and immunity of Tibetan sheep.Twenty-four male sheep?9 months old?with similar body weight were randomly divided into 4 groups?6 of each group?,and fed a basal diet with four levels of Astragalus membranaceus root powder?AMT?based on the daily dry matter intake?A₀:0%,A₂:2%,A₅:5%and A₈:8%?.The measurements were recorded over a 70-d feeding period,with 14-d adaptation.Sheep fed with AMT showed higher average daily gain?ADG?and lower feed/gain ratio?F/G?than controls?P<0.001?.The carcass weight and slaughter rate of the Tibetan sheep were significantly higher with the inclusion of the AMT than A₀.The rumen concentrations of NH₃-N?P<0.001?,total volatile fatty acids?TVFA??P=0.028?,acetate?P=0.017?and propionate?P=0.031?in A₅ and A₈ groups were higher than A₀.The addition of AMT in the feed significantly increased serum antioxidant and immunity indexes of the sheep and increased the concentrations of serum interleukin,immunoglobulin,tumour necrosis factor-??TNF-???P=0.010?.The addition of AMT to Tibetan sheep also significantly improved the rumen microflora function,which is more conducive to the digestion and utilization of fiber.With the increase of AMT addition,the relative abundance of Firmicutes increased significantly?P<0.05?,and the Bacteroidetes relative abundance significantly decreased?P<0.05?.Astragalus addition improved the antioxidant properties of serum,meat and intestinal mucosa of Tibetan sheep.The contents of catalase?CAT,P=0.031?and superoxide dismutase?SOD,P=0.033?of meat in A₅ and A₈ groups were significantly higher than the other two groups.The total antioxidant capacity?T-AOC,P=0.041?and superoxide dismutase content?SOD,P=0.002?in the intestinal mucosa of groups A₅ and A₈ were significantly higher than A₀ and A₂.In conclusion,AMT can be used as a feed additive to improve growth performance and rumen fermentation,immunity and antioxidant capacity of Tibetan sheep.The current study showed that the optimum proportion of AMT in the diet of Tibetan sheep is 5%to 8%of DMI.