Dynamic Changes In Rumen Bacteria And Metabolites In Dairy Cows During Periparturient Period And Their Relationship With Postpartum Ketosis

Dairy cows undergo different physiological stages from pregnancy to delivery and lactation during the peripartum period,and their physiology and metabolism change dramatically,making them vulnerable to negative energy metabolism diseases such as ketosis and fatty liver.Ruminal microbial communities play an important role in energy homeostasis,metabolism and physiological adaptation in dairy cows,and changes in ruminal flora during the peripartum period are closely related to the occurrence of ketosis in the late peripartum period.However,there is still a lack of in-depth understanding of the dynamics of rumen bacteria and metabolites in dairy cows during the peripartum period and their relationship with ketosis in the late peripartum period.In this study,70 healthy Holstein cows with body condition scores of 3-4 and 2-5 litters entering the perinatal period were selected to investigate the characteristics of rumen bacterial community composition and rumen metabolites at different stages of perinatal period and their relationship with ketosis in the late perinatal period.Blood and rumen fluid were collected from cows at eight time points,including before parturition(-21 d,-14 d,-7 d),on the day of parturition(3 d,7 d,14 d,21 d)and after parturition(3 d,7 d,14 d,21 d),and blood biochemical indexes such as BHBA were monitored.The changes in rumen flora and rumen metabolites in cows with ketosis were correlated with blood biochemical indices,and the relationship between changes in rumen flora and rumen metabolites and the occurrence of ketosis in cows in the peripartum period was initially elucidated.The following results were obtained from these studies:1.ketosis mainly occurred in the late perinatal period,with the highest incidence at 7 d postpartum,and the incidence of subclinical ketosis was significantly higher than that of clinical ketosis at all time points.BHBA,NEFA,AST,T-BIL and D-BIL were significantly higher in the blood of ketotic cows in the late perinatal period than in healthy cows.The alpha diversity of the rumen flora of ketosis cows did not change significantly at most time points compared to healthy cows,but the structure of the flora was significantly altered.The core flora of the rumen of periparturient cows changed significantly over time,with similar trends at the phylum level for both groups of cows at adjacent time points,but the species composition of the flora changed significantly at both the phylum and genus levels.Compared to healthy cows,ketosis cows showed significant changes in the species composition of the rumen flora at each time point,with significantly higher abundance of the core rumen flora Prevotella,Rikenellaceae_RC9_gut_group,etc.in the late periparturient period.At the peak of ketosis,the rumen of ketotic cows was significantly enriched in the phylum Prevotella,order Bacillus,order Negativicutes,order Acidaminococcales,genus Succiniclasticum,etc.Prevotella ruminicola was significantly enriched in the rumen.The relative abundance of Prevotellaceae_UCG-001 and Prevotellaceae_UCG-003 showed highly significant positive correlation(P<0.01)with blood BHBA,AST,NEFA,DBIL and TBIL,and highly significant negative correlation(P<0.01)with blood GLU.Lachnospiraceae_XPB1014_group and Defluviitaleaceae_UCG-011 were significantly positively correlated(P<0.05).2.The results of periparturient rumen fluid broad-target metabolomic analysis showed that the structural differences in rumen metabolite composition between healthy and ketotic cows were not significant before parturition,but the differences were significant from 7 to 21 d after parturition,with significant changes in the metabolic profile of rumen fluid in ketotic cows.A total of 187 differential metabolites,including lipid and lipid-like molecules,organic acids and their derivatives,amino acids and their metabolites,and organic oxygen compounds,were screened from the rumen fluid of ketosis cows at seven different time points(7 d postpartum was not screened),with most of the differential metabolites on the day of parturition and 7-21 d postpartum.the differential metabolites at 7-21 d postpartum were mainly involved in rumen metabolism of vitamin B6,L-Norleucine,Choline,Methiionine,Daidzein and Lipoamide were associated with the Lachnospiraceae_NK3A20_group,the Christensenellaceae_RK3A20_group,and the Lachnospiraceae_NK3A20_group,Christensenellaceae_R-7_group,Acetitomaculum,Methanobtrvibacter,Olsenella,Prevotellaceae_UCG-001,NK4A214_group,Succinivibrionaceae UCG 002 showed significant or highly significant positive correlations(P<0.05 or P<0.01).methylpalmitiate showed significant or highly significant positive correlations with Prevotella,Prevotellaceae_UCG-001,Prevotellaceae_UCG-003(P<0.05 or P<0.01),Lipoamide showed significant negative positive correlation with Rikenellaceae_RC9_gut_group(P<0.05),and Lipoamide,N6-Acetylcholine showed significant positive correlation with Lachnospiraceae_XPB 1014_group(P<0.05).Olsenella,Christensenellaceae_R-7_group,Succinivibriona,Methanobtrvibacter showed significant or highly significant positive correlations(P<0.05 or P<0.01)with a larger number of differential metabolites.Among them,Prevotellaceae_UCG-001 and Prevotellaceae_UCG-003 showed highly significant positive correlations with BHBA,NEFA,AST,D-BIL and TBIL in the blood of cows at the peak of ketosis(P<0.01)and significant negative correlations with GLU(P<0.05)...