Comparative study on methane production and methanogenic bacteria diversity of high-yielding and low-yielding dairy cows.

By exploring the variation rules of methane production and methanogenic bacteria diversity in different lactation stages of high and low producing dairy cows, the experiment revealed the reasons for the difference in methane production between high and low-yielding dairy cows from the perspective of changes in rumen microbial flora structure, and analyzed the correlation between the relative abundance of methanogenic bacteria and methane production, milk yield and milk quality. A two-factor design was used in the experiment. A total of 36 Holstein cows with good health, similar weight, parity and feeding management conditions were selected. According to the lactation performance (high-yielding, low-yielding) and lactation stage (early stage, middle stage and late stage), they were divided into the high-yielding pre-lactation group, high-yielding mid-lactation group, high-yielding late lactation group, low-yielding pre-lactation group, low-yielding mid-lactation group, and low-yielding late lactation group, with six cows in each group. All cows were fed the same fully mixed diet. A methane production prediction model was used to calculate the methane production, and the diversity of rumen methanogens was determined by high-throughput sequencing technology. The results showed that the methane production of the high-yielding cows was significantly lower than that of the low-yielding cows (P<0.05), and the methane production of cows in early lactation was significantly higher than that in the middle and late lactation (P<0.05). The Shannon index of rumen methanogens in the high-yielding dairy cows was significantly lower than that in the low-yielding dairy cows (P<0.05), while the Ace index, Chao index, and Simpson index were not significantly different from those of low-yielding dairy cows (P>0.05). The relative abundance of Methanosphaera in the rumen of the high-yielding dairy cows was significantly higher than that of the low-yielding dairy cows (P<0.05), and the relative abundance of Methanobrevibacter in the rumen of the high-yielding dairy cows was significantly lower than that of the low-yielding dairy cows (P<0.05). The relative abundance of rumen Methanosphaera in the early and middle lactation period was significantly higher than that in the late lactation period (P<0.05), and the relative abundance of Methanobrevibacter in the late lactation period was significantly higher than that in the early and middle lactation period (P<0.05). The relative abundance of Methanosphaera in the rumen of the dairy cows was negatively correlated with methane production and milk fat percentage (P<0.05), and positively correlated with milk yield (P<0.05). The study indicates that the methane production and relative abundance of the rumen Methanobrevibacter in the high-yielding cows are lower than those in the low-yielding cows, and the methane production in the early lactation is higher than that in the middle and late lactation. [ABSTRACT FROM AUTHOR]