| The dry matter intake of dairy cows after delivery is still at a low level.In addition,the energy output is greater than the energy intake due to the start of lactation,which is prone to negative energy balance(NEB),resulting in an increased incidence of metabolic disorders or inflammatory diseases in the postpartum period.About 70%of the energy in dairy cows is supplied by metabolites produced by rumen microbial fermentation feed.Changes in microorganisms are greatly correlated with NEB and changes in postpartum diseases associated with NEB.Therefore,this experiment explored the changes of rumen microorganisms and their metabolites in postpartum dairy cows,in order to provide more biological information for the pathogenesis of postpartum NEB and NEB related diseases.In a large farm in Ningxia,10 healthy Holstein cows were randomly selected to collecte rumen juice before feeding on the morning of 0,7,14 and 21 days postpartum.Relative abundance of rumen microorganisms and concentration of metabolites of dairy cows after delivery were detected by 16S rRNA high-throughput sequencing,GC-MS/MS,and UPLC-MS/MS metabolomics,respectively.The results of the test are as follows:1.The results of rumen microorganisms study showed that the relative abundance of Euryarchaeota and Chloroflexi of phylum level at 7 days postpartum were significantly lower than that at 0 days postpartum.The relative abundances of Methanobrevibacter,Flexilinea and unclassified_Christensenellaceae of genus level were significantly lower than those at 0 day postpartum,while the relative abundances of unclassified_Ruminococcaceae,unclassified_Prevotellaceae,Moryela and Pseudobutyricibrio were significantly higher than those at 0 day postpartum.The relative abundance of unclassified_Ruminococcaceae,Moryela and unclassified_Christensenellaceae of genus level at 14 days postpartum was significantly lower than that at 7 days postpartum,and the relative abundance of Olsenella and Sharpea was significantly higher than that at 7 days postpartum.There was no significant difference in microorganisms between 14 and 21 days postpartum.2.The results of rumen short chain fatty acids showed that the concentration of propionic acid,butyric acid and valeric acid at 7 days postpartum were significantly higher than those at 0 days postpartum,but there were no significant changes in acetic acid,isobutyric acid,isovaleric acid and caproic acid.There were no significant changes in the content of acetic acid,propionic acid,isobutyric acid,butyric acid,isovaleric acid,valeric acid and caproic acid from 7 to 21 days postpartum.The correlation analysis between microorganisms and SCFAs showed that there was a significant negative correlation between Euryarchaeota and propionic acid at 0-7 days postpartum.There was a significant negative correlation between Chloroflexi and propionic acid and valeric acid.There was a significant negative correlation between Methanobrevibacte and propionic acid,and a significant positive correlation between unidentified_Prevotellaceae and propionic acid,butyric acid and valeric acid.There was a significant positive correlation between Pseudobutyrivibrio and butyric acid,a significant positive correlation between unidentified_Ruminococcaceae and propionic acid,and a significant positive correlation between Moryela and propionic acid.3.The results of rumen metabolites showed that the concentration of 27 metabolites increased significantly and 35 metabolites decreased significantly at 7 days postpartum compared with 0 days postpartum.Compared with 7 days postpartum,the concentration of 18 metabolites increased significantly and 4 metabolites decreased significantly at 14 days postpartum.Compared with 14 days postpartum,the concentration of 3 metabolites increased significantly and 8 metabolites decreased significantly at 21 days postpartum.Among these differential metabolites,the concentration of lactose,D-glucose,tyramine and adenine increased significantly from 0 to 14 days postpartum and decreased significantly from 14 to 21 days postpartum,while the concentration of pyridoxal decreased significantly from 0 to 7 days postpartum,increased significantly from 7 to 14 days postpartum,and gradually decreased to the level of 7 days postpartum after 14 days.Conclusion:the rumen microorganisms of healthy dairy cows changed significantly at 0-7 days after delivery,and the concentration of metabolites and SCFAs also changed responsively,indicating that the change of rumen microflora is closely related to NEB.Rumen microorganisms and their metabolites did not change significantly at 7-21 days postpartum,suggesting that NEB of dairy cows is easy to occur at 0-7 days postpartum. |
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