High-producing dairy cows face varying degrees of metabolic stress and challenges during the late perinatal period, resulting in ruminal bacteria abundance and their fermentative ability occurring as a series of changes. However, the dynamic changes are still not clear.
Ten healthy, high-producing Holstein dairy cows with similar body conditions and the same parity were selected, and ruminal fluid from the dairy cows at postpartum 0, 7, 14, and 21 d was collected before morning feeding. 16S rRNA high-throughput sequencing, GC-MS/MS targeted metabolomics, and UPLC-MS/MS untargeted metabolomics were applied in the study to investigate the dynamic changes within 21 d postpartum.
The results displayed that the structures of ruminal bacteria were significantly altered from 0 to 7 d postpartum ( R = 0.486, P = 0.002), reflecting the significantly declining abundances of Euryarchaeota and Chloroflexi phyla and Christensenellaceae, Methanobrevibacter, and Flexilinea genera ( P < 0.05) and the obviously ascending abundances of Ruminococcaceae, Moryella, Pseudobutyrivibrio, and Prevotellaceae genera at 7 d postpartum ( P < 0.05). The structures of ruminal bacteria also varied significantly from 7 to 14 d postpartum ( R = 0.125, P = 0.022), reflecting the reducing abundances of Christensenellaceae, Ruminococcaceae, and Moryella genera ( P < 0.05), and the elevating abundances of Sharpea and Olsenella genera at 14 d postpartum ( P < 0.05). The metabolic profiles of ruminal SCFAs were obviously varied from 0 to 7 d postpartum, resulting in higher levels of propionic acid, butyric acid, and valeric acid at 7 d postpartum ( P < 0.05); the metabolic profiles of other ruminal metabolites were significantly shifted from 0 to 7 d postpartum, with 27 significantly elevated metabolites and 35 apparently reduced metabolites ( P < 0.05). The correlation analysis indicated that propionic acid was positively correlated with Prevotellaceae and Ruminococcaceae ( P < 0.05), negatively correlated with Methanobrevibacter ( P < 0.01); butyric acid was positively associated with Prevotellaceae, Ruminococcaceae, and Pseudobutyrivibrio ( P < 0.05), negatively associated with Christensenellaceae ( P < 0.01); valeric acid was positively linked with Prevotellaceae and Ruminococcaceae ( P < 0.05); pyridoxal was positively correlated with Flexilinea and Methanobrevibacter ( P < 0.05) and negatively correlated with Ruminococcaceae ( P < 0.01); tyramine was negatively linked with Ruminococcaceae ( P < 0.01).