Comparative Study On Rumen Microflora Structure And Serum Biochemical Indexes Of High And Low Yield Dairy Cows

Rumen microorganism has significant influence on the performance of dairy cows,but there are relatively few literatures on the difference of rumen microflora between high-yield and low-yield dairy cows.In this experiment,12 healthy,similar parity（2.04±0.81）,similar lactation days（23.58±8.80 d）and similar body weight high-yield（40.56± 1.57 kg/d）and low-yield Holstein dairy cows（25.17± 1.66 kg/d）were selected and divided into two groups:high-yield group and low-yield group.The rumen flora diversity and blood biochemical indexes were compared and analyzed,and the test results were as follows:Experiment 1:The difference of rumen fermentation parameters between high and low yield dairy cows.The results showed that there were no significant differences in pH,volatile fatty acids,acetic acid and microbial protein concentrations between high and low yield groups（P>0.05）.The concentration of butyric acid in rumen of high-yield group was significantly higher than that of low-yield group（P<0.05）,and the concentration of propionic acid was extremely significantly higher than that of low-yield group（P<0.01）.The acetic acid/propionic acid value and ammonia nitrogen concentration in rumen of low-yield group were significantly higher than those of high-yield group（P<0.01）.Experiment 2:Study on the difference of rumen bacterial community structure between high-yield and low-yield dairy cows.The results showed as follows:At the phylum level,the dominant phyla in the rumen of high-yield and low-yield dairy cows were Firmicutes and Bacteroidetes.The abundance of Firmicutes in rumen of high-yielding cows was significantly lower than that of low-yielding cows（P<0.05）,and the abundance of Cyanophyta was significantly higher than that of low-yielding cows（P<0.05）.The abundance of Saccharibacteria in the rumen of low-yielding cows was significantly higher than that of high-yielding cows（P<0.01）.There were no significant differences in Bacteroidetes,Proteobacteria,SRI_absconditabacteria,Tenericutes Actinobacteria,and Spirochaetae between the high yield group and the low yield group（P>0.05）.At the genus level,The dominant genera in rumen of high and low yield dairy cows are Prevotella.The relative abundance of Ruminococcus and Prevotella in the rumen of high-yield cows was not significantly different from that of low-yield cows（P>0.05）.The relative abundance of Prevotella₇,Syntrophococcus and Roseburia in high yield group was significantly higher than that in low yield group（P<0.01）.The abundance of Rikenellaceae_RC9_gut_group and Ruminococcaceae_NK4A214_group in low-yielding group was significantly higher than that in high-yielding group（P<0.05）.The abundance of Christensenellaceae_R-7_group,Lachnosp iraceae_XPB1014_group,Saccharofermentans,Candidatus_Saccharimonas,Family_ⅩⅢ_AD3011_group,Clostridiales_unclassified,Bacteroidales_BS11_gut_group_norank,Ruminococcaceae_UCG-011 and Ruminococcaceae_unclassified were significantly higher than those of high-yielding cows（P<0.01）.In the correlation analysis between rumen flora and rumen volatile acid,there was a significant correlation between Prevotella₇ and propionate butyric acid（P<0.05）,and a significant negative correlation between Rikenellaceae_RC9_gut_group and propionate（P<0.05）.There was a significant negative correlation between Lachnospiraceae XPB1014_group and butyric acid（P<0.05）.Experiment 3:Comparison of serum biochemical indexes between high and low yield dairy cows.The results showed as follows:in the biochemical indexes related to lipid metabolism,the concentration of LDL cholesterol in high yield group was significantly higher than that in low yield group（P<0.05）.The concentrations of high density lipoprotein cholesterol and total cholesterol in high yield group were significantly higher than those in low yield group（P<0.01）.Among the biochemical indexes related to antioxidant,the concentration of malondialdehyde（MDA）in high yield group was significantly higher than that in low yield group（P<0.05）,and the total antioxidant capacity（T-AOC）in high yield group was significantly increased compared with that in low yield group（P<0.01）.There was no significant difference in the biochemical indexes related to liver function between high-yield and low-yield cows（P>0.05）.In conclusion,compared with low-yielding dairy cows,the rumen fermentation butyric acid and propionic acid concentrations of high-yielding dairy cows were higher,the rumen Firmicutes abundance was significantly lower than that of low-yielding dairy cows,and the rumen Cyanobacteria abundance was significantly higher than that of low-yielding dairy cows.Prevotella was the dominant genus in rumen of high-yield and low-yield dairy cows,and the relative abundance of Prevotella₇ in rumen of high-yield dairy cows was significantly higher than that of low-yield dairy cows.The concentrations of lipid metabolism and antioxidant indexes in blood of high-yield cows were higher than those of low-yield cows.