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Alterations in ruminal and fecal microbial communities of dairy cows during ketosis.

Q. Wang




Alterations in ruminal and fecal microbial communities of dairy cows during ketosis.
Q. Wang*1, W. Bao1, Y. Cui1, J. J. Loor2, B. Gao1, Y. Ren1, C. Xu1. 1College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University Daqing, Heilongjiang, China, 2Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois Urbana, IL.

The objective of this study was to simultaneously investigate the profiles of rumen and fecal microbiome in cows afflicted by clinical ketosis. Twenty-seven Holstein dairy cows of similar age, parity and body condition score were used in the study. Blood hydroxybutrate concentration was 4.1 � 0.72 mmol/L in ketotic cows, 1.36 � 0.12 mmol/L in subclinical ketotic cows, and 0.88 � 0.14 mmol/L in healthy control cows. Rumen fluid and fecal samples were all collected at 21 d postpartum in the morning within 2 h before feeding. An oral tube with a syringe was used for rumen sampling, while fecal samples were collected via rectal grab. Bacterial communities were identified by 16S rRNA sequencing. We found that the microbial structure, composition and diversity were different in rumen and feces and affected by ketosis compared with healthy dairy cows. More OTU encompassing bacterial genus and species were detected in rumen fluid than feces among dairy cows in the 3 groups. Compared with healthy cows, both species richness and evenness were higher in rumen fluid from clinical and subclinical ketotic cows. Microbial composition in rumen fluid and feces differed between ketotic and healthy cows. Regardless of ketotic status, principal component analysis (PCA) revealed that there were more differences at the phyla and genus level between rumen fluid and feces. Regardless of health status, microbial composition distribution at the phylum level revealed that Firmicutes, Prevotella, Bacteroidetes, Clostridiales, Lachnospiraceae were the top 5 dominant species in rumen fluid and fecal samples. A total of 38 bacteria were detected as dominant species in which Prevotella and Butyrivibrio were the top 2 commensal bacteria in rumen fluid.Overall, the Clinical-ketosis group was significantly enriched for the genera Rumenococcaceae, BS11, RF16, Christensenellaceae, Anaeroplasma and Mogibacteriaceae when compared with the healthy group. Hence, ketosis increased the diversity of bacteria with important roles in metabolism of amino acids and energy substrates in rumen fluid.

Keywords: ketosis, rumen fluid, bacterial structure.