Abstract

At present, research on high-concentrate (HC) diets mostly focused on the rumen, and there is a paucity of information on the hindgut microbiota of dairy cows. In the present study, a 2 × 2 crossover design with four healthy Holstein cows was used, and the metagenomics approach was adopted to reveal the remodeling effects of HC diets on hindgut microbiota and their metabolic functions. Results showed that, compared with the low-concentrate (LC) diets, HC diets have markedly decreased (p < 0.05) the abundance of cellulolytic bacteria (such as Fibrobacter, Ruminococcus, and Ruminiclostridium) and methanogens (such as Methanobrevibacter, Methanosarcina, and Methanosphaera); and correspondingly, HC diets have significantly reduced (p < 0.05) the abundance of carbohydrate-active enzymes (CAZy) related to hemicellulases (GH10, GH11, and GH54) and cellulases (GH1, GH44, and GH45) and increased the abundance of one oligosaccharide-degrading enzyme (GH32). Furthermore, 62 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of hindgut microbiota were affected (p < 0.05) by different dietary treatments, and the major pathways altered by HC diets were “Methane metabolism” (enriched in the LC group), “Lipid metabolism” (enriched in the HC group), and several sub-pathways in “Amino acid metabolism” (such as Phenylalanine metabolism, and Phenylalanine, tyrosine, and tryptophan biosynthesis). Also, the microbial genes involved in the pathways “Methane metabolism” (except 1 gene), “Tryptophan metabolism”, and “Phenylalanine metabolism” were all decreased (p < 0.05) in the present study. These findings suggested that HC diets caused the remodeling of hindgut microbiota and its potential functions, and these results may benefit in gaining a deeper understanding of the impact of HC diets on the hindgut microbiota of dairy cows.

Highlights

  • The gastrointestinal tract-dwelling microbiota is central to nutrient digestion, production performance, and host health [1, 2]

  • We evaluated the effects of HC diets on the fecal microbial communities at different taxonomic levels

  • We found the relative abundance of genera Methanosarcina and Methanosphaera (

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Summary

Introduction

The gastrointestinal tract-dwelling microbiota is central to nutrient digestion, production performance, and host health [1, 2]. As compared with the multilayer squamous epithelium of rumen, the singlelayer columnar epithelium of the hindgut is more fragile and susceptible to this potentially dangerous environment, which further damaged the host health and production performance [11, 12]. In addition to the host health, the enteric microbiota of dairy cows is related to food safety, fecal pollution and is identified as the source of various microbial contamination, such as soil and water reservoirs [13, 14]. Enriching the information about fecal microbiome and the remodeling effects of HC diets could contribute to host health and environmental optimization and provide the possibility to use the characteristic microbial changes to reflect the effects of HC diets on the host response of dairy cows in the future

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