This study was conducted to investigate the effects of mulberry leaf flavonoids ( MLF) and resvera-trol ( Res) on gas metabolism and methane emission in mutton sheep, with an aim to determine the optimum supplemental levels.Fifteen healthy Dorper ( ) ×Thin-Tailed Han (♀) crossbreed sheep ( F1 ) weighted (60.0 ±1.73) kg with similar age were selected in a single factor experimental design.The experiment consis-ted of control period, experimental periods Ⅰ and Ⅱ.Control period: fifteen sheep were fed a basal diet ( without supplementation, control group, n=15);experimental periodⅠ:fifteen sheep were randomly allot-ted to five groups ( n=3) , and MLF supplemental levels were 0.25, 0.50, 1.00, 2.00 and 4.00 g/d, respec-tively; experimental period Ⅱ: fifteen sheep were randomly allotted to five groups ( n=3) , and Res supple-mental levels were 0.125, 0.250, 0.500, 1.000 and 2.000 g/d, respectively.Each period lasted for 16 days, which was consisted of a 7-day pre-experimental period and a 9-day experimental period.Open-cycle Sable cal-orimetry system was used for gas metabolism test.The results showed as follows: the supplementation of 2.00 g/d MLF and 0.250 g/d Res decreased 6.38%( P>0.05) and 10.11%( P<0.05) of methane emission per kilogram of dry matter intake calculated based on metabolic weight, respectively.In conclusion, natural plant extractions MLF and Res can affect gas metabolism and reduce methane emission at some extent; under conditions in the present study, the optimum supplemental levels of MLF and Res are 2.00 and 0.250 g/d, re-spectively, considering the inhabitation on methane emission.%本试验旨在研究天然植物提取物桑叶黄酮（ MLF ）和白藜芦醇（ Res ）对肉羊气体代谢及甲烷排放的影响，并筛选出它们的最适宜的添加水平。选取15只体重为（60．00±1．73） kg、年龄相近、体况良好的杜泊绵羊（）×小尾寒羊（♀）杂交F1代肉用成年母羊作为试验动物。试验采用单因素试验设计，包括对照期以及试验期Ⅰ和Ⅱ。对照期：15只羊均饲喂基础饲粮（0添加水平，对照组，n＝15）；试验期Ⅰ：将15只羊随机分为5组（n＝3），MLF添加水平分别为0．25、0．50、1．00、2．00和4．00 g/d；试验期Ⅱ：将15只羊随机分为5组（n＝3），Res添加水平分别为0．125、0．250、0．500、1．000和2．000 g/d。每期试验16 d，其中预试期7 d，正试期9 d。采用Sable开路式循环测热系统进行气体代谢试验。结果表明：与对照组相比，MLF添加水平为2．00 g/d时，代谢体重基础上每千克干物质采食量的甲烷排放量降幅最大，但差异不显著（P＞0．05），Res添加水平为0．250 g/d时，显著降低了代谢体重基础上每千克干物质采食量的甲烷排放量（ P＜0．05），降幅分别为6．38％、10．11％。结果提示，天然植物提取物MLF和Res可以在一定程度上影响肉羊的气体代谢并降低甲烷排放量；本试验条件下，MLF和Res抑制甲烷排放效果最佳的添加水平分别为2．00、0．250 g/d。
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