Comparative Study On Rumen Bacteria Quantity And Diversity Of Dairy Cows In Different Physiological Stages

In this study,we explored the effects of different physiological stages on rumen bacteria?General bacteria,R.albus,R.flavefaciens,F.succinogenes,B.fibrisolvens,S.bovis a-nd Prevotella Ruminobacter amylophilus?in dairy cows.At the same time,we explored the changes of bacterial diversity in rumen fluid of dairy cows at different physiological stages by 16S rRNA high-throughput sequencing technology.In addition,we also determined the effects of different physiological stages on rumen fermentation function and apparent digestibility in dairy cows.In this study,we selected five groups Holstein cows,which were being in early prenatal stage,early lactation stage,mid lactation stage,late lactation stage and dry milk stage.Rumi-nal chyme was collected to determine the quantity of eight rumen bacteria,rumen bacterial diversity and rumen fermentation function at different physiological stages.Diets and feces were collected to measure the apparent digestibility of dairy cows in whole digestive tract at different physiological stages.The results showed that:?1?The numbers of R.flavefaciens,F.succinogenes and General bacteria decreased significantly?P<0.05?,when cows reached to the lactation stage,then these numbers significantly increased?P<0.05?at dry milk stage,and became similar to those in early prenatal stage?P>0.05?.The trend of changes in the number of S.bovis,Prevotella Ruminobacter amylophilus were opposite.There was no significant difference in the number of R.albus and B.fibrisolvens at different physiological stage?P>0.05?.The number of F.succinogenes and General bacteria were significantly higher in early lactation stage than in medium lactation stage and late lactation stage?P<0.05?,and there was no significant difference between mid-lactating and lactation?P>0.05?,The trend of changes in the number of amylin-resistant amylolytic bacteria was opposite.There was no significant difference in the number of R.flavefaciens,S.bovis and Prevotella at different lactation stage?P>0.05?.?2?The rumen bacteria diversity decreased significantly?P<0.05?,when cows reached to early lactation stage.After reaching to dry milk stage,the rumen bacteria diversity significantly increased?P<0.05?,and became similar to that in early prenatal stage?P>0.05?.Rumen bacterial diversity was significantly higher in early lactation stage than in medium lactation stage and late lactation stage?P<0.05?.And there was no significant difference between the medium lactation stage and the late lactation stage?P>0.05?.?3?At phyla level,the dominant rumen bacteria in early prenatal stage and dry milk stages were Bacteroidetes and Firmicutes,and in the lactation period,the dominant rumen bacteria were Bacteroidetes,Proteobacteria and Firmicutes.At family level,the dominant rumen bacteria in early prenatal stage and dry milk stage was Prevotellaceae,and in the lactation period,the dominant rumen bacteria were Succinivibrionaceae and Prevotellaceae.?4?The relative abundance of Bacteroidetes,SR1,Tenericutes,TM7,Fibrobacteres,Actinobacteria,Prevotellaceae,and Ruminococcaceae decreased significantly?P<0.05?,whe-n cows reached to early lactation stage.And there was no significant difference at different lactation stages?P>0.05?.After reaching to dry milk stage,the relative abundance of these bacteria increased significantly?P<0.05?,and became similar to those in early prenatal stage?P>0.05?.The trend of change of Proteobacteria and Succinivibrionaceae were opposite.The relative abundance of Firmicutes and Lachnospiraceae were not significantly different at different physiological stage?P>0.05?.?5?Through PcoA analysis,it was found that cows had similar bacteria composition in early prenatal stage and dry milk stage,which were different from the bacteria composition in lactation stage.The compositions of rumen bacteria were similar in the middle lactation stage and late lactation stage,which were different from those in early lactation stage.?6?The relative abundance of Selenomonas in the rumen of dairy cows was positively correlated with milk fat rate?r=0.58,P<0.05?,and the relative abundance of Rossia was significantly negatively correlated with lactose rate?r=-0.59,P<0.05?.?7?The concentration of NH₃-N in rumen of dairy cows had no significant difference at different physiological stages?P>0.05?.The pH value and the concentration of MCP,acetic acid,isobutyric acid,butyric acid,isovaleric acid,TVFA and acetic acid/propionic acid ratio decreased significantly?P<0.05?,when cows reached to early lactation stage.After reaching to dry milk stage,these parameters were significantly increased?P<0.05?,and became similar to those in early prenatal stage?P>0.05?.The trend of changes in concentration of propionic acid and valeric acid were opposite.Comparing different lactation stages,there were no significant difference in pH value and the concentration of TVFA during lactation stages?P>0.05?.The concentration of MCP,isobutyric acid and isovaleric acid in early lactation stage were significantly higher than those in mid and late lactation stages?P<0.05?,and there was no significant difference in mid and late lactation stages?P>0.05?.The concentration of acetic acid and the acetic acid/propionic acid ratio in late lactation stage were significantly higher than those in early and mid lactation stages?P<0.05?,And there was no significant difference between early lactation stage and the mid lactation stage?P>0.05?.The concentration of propionic acid in mid lactation stage was significantly higher than those in late lactation stages?P<0.05?,and it was similar to that in early lactation stages?P>0.05?.As for the concentration of propionic acid,there was no significant difference between mid lactation stage and late lactation stages?P>0.05?.The concentration of butyric acid in mid lactation stage was significantly lower than those in early and late lactation stages?P<0.05?.And there was no significant difference between early lactation stage with late lactation stage?P>0.05?.The trend of changes in concentration of valeric acid were opposite from butyric acid.?8?The apparent digestibility of OM and DM increased significantly?P<0.05?,when cows reached to early lactation stage.Which showed no significant difference during lactation stages?P>0.05?.After reaching to dry milk stage,the apparent digestibility of OM and DM were significantly decreased?P<0.05?,and bacame similar to those in early prenatal stage.The apparent digestibility of NDF had opposite trend from OM and DM.The apparent digestibility of ADF in mid lactation stage was significantly lower than those in early prenatal stage and dry milk stages?P<0.05?,and be similar to those in early lactation stage and late lactation stage.And there was no significant difference between early prenatal stage,early lactation stage,late lactation stage and dry milk stage?P>0.05?.