Effects of different ratio of total net energy requirement to nitrogen in ration on health and rumen bacterial diversity and function in Yak

The purpose of this experiment was to study the effect of growth performance, blood biochemical indexes, rumen fermentation parameters and rumen bacterial community structure for yak under the condition of different ratio of total net energy requirement to nitrogen in ration(NEmf/N). The study selected 36 male yaks aged about 2-3 years old with similar body condition, which were divided into three groups based on the different NEmf/N. The ration were categorized as high, medium and low NEmf/N. The actual NEmf/N obtained in this study decreased from high to low NEmf/N groups with a value of 6.92, 5.81 and 5.19 MJ/kg (Group H, M, L), respectively. The results showed that:1) Compared with group H, group M showed better production performance, rumen fermentation mode and higher rumen bacterial diversity and richness. It was mainly manifested in the significantly higher average daily weight gain, significantly lower ratio of acetate and propionate and higher content of total volatile fatty acids in group M; 2) Compared with group L, group M showed higher energy conversion efficiency and healthier condition. It was mainly manifested in the significantly higher blood glucose content, lower urea content and lower lactate dehydrogenase, creatine kinase content in group M; 3) In summary, yaks subjected to 5.81 MJ/kg NEmf/N achieved superior performance.