Assessment of rumen bacteria in dairy cows with varied milk protein yield

摘要

The present study was conducted to assess rumenbacteria in lactating cows with different milk proteinyield, aiming to understand the role of rumen bacteriain this trait. Cows with high milk protein yield (highmilk yield and high milk protein content, HH; n = 20)and low milk protein yield (low milk yield and lowmilk protein content, LL; n = 20) were selected from374 mid-lactation Holstein dairy cows fed a high-graindiet. Measurement of the rumen fermentation productsshowed that the concentrations of ruminal total volatilefatty acids, propionate, butyrate, and valerate and theproportion of isobutyrate were higher in the HH cowsthan in the LL cows. Amplicon sequencing analysis ofthe rumen bacterial community revealed that the richness(Chao 1 index) of rumen microbiota was higherin the LL cows than in the HH cows. Among the 10predominant bacterial phyla (relative abundance being＞0.10%, present in ＞60% of animals within eachgroup), the relative abundance of Proteobacteria was1.36-fold higher in the HH cows than in the LL cows.At the genus level, the relative abundance of Succinivibriowas significantly higher and that of Clostridiumtended to be higher in the LL cows than in the HHcows. Sharpea was 2.28-fold enriched in the HH cowscompared with the LL cows. Different relationships betweenthe relative abundances of rumen microbial taxaand volatile fatty acid concentrations were observed inthe HH and the LL animals, respectively. Succinivibrioand Prevotella were positively correlated with acetate,propionate, and valerate in the LL cows, whereasSharpea was positively correlated with propionate andvalerate concentrations in the HH cows. Collectively,our results revealed that rumen bacterial richness andthe relative abundances of several bacterial taxa significantlydiffered between dairy cows with high andlow milk protein yields, suggesting the potential rolesof rumen microbiota contributing to milk protein yieldin dairy cows.