Dietary supplementation with mulberry leaf flavonoids inhibits methanogenesis in sheep

The effects of flavonoids on methanogenesis and microbial flora in Dorper × thin‐tailed Han crossbred ewes were evaluated in two experiments. To investigate the effects of flavonoids on nutrient digestibility and nitrogen balance, 18 ewes (60.0 ± 1.73 kg body weight (BW)) were allotted to two dietary treatments in experiment one, a control diet and the control diet supplemented with flavonoids (2 g/head/day). In experiment two, the effects of supplementary flavonoids on ruminal fermentation and microbial flora were investigated using quantitative polymerase chain reaction with six ewes (67.2 ± 0.79 kg BW) with ruminal cannula assigned to the identical dietary treatments used in experiment one. Supplementary flavonoids improved the apparent digestibility of nitrogen (N, P  < 0.001) and neutral detergent fibre (NDF, P  = 0.024) and decreased daily CH 4 output ( P  < 0.001). The ruminal pH ( P  = 0.638) and ammonia ( P  = 0.690) were not affected by supplementary flavonoids, whereas the total volatile fatty acid (VFA) content increased ( P  = 0.037). Supplementary flavonoids decreased ruminal populations of protozoans ( P  = 0.002) and methanogens ( P  < 0.001) and increased the populations of Fibrobacter succinogenes ( P  = 0.016). In conclusion, flavonoids improved the digestibility of organic matter and reduced CH 4 output by inhibiting the populations of microbes involved in methanogenesis.