Effects of different fiber levels of energy feeds on rumen fermentation and the microbial community structure of grazing sheep.

Abstract

Background: Rumen microbial community structure and stability are very important for ruminant health, growth and development, and livestock product yield. Dietary composition and nutritional structure affect microbial diversity and richness. The purpose of this study was to evaluate the effects of different fiber levels of energy feed on the rumen microflora and fermentation function of grazing sheep in salinized sown pasture, to reveal the response of the main microflora of sheep rumen at the phylum and genus levels to different fiber levels of energy feed and to analyze the internal mechanism to provide a reference for the selection of energy feed and the improvement of the production performance of grazing livestock.

Results: The fiber level of energy feed affects the rumen fermentation and rumen microbial community structure of grazing sheep. Low-fiber-energy feeds significantly increased the relative abundance of Actinobacteria, while the relative abundances of Cyanobacteria, Ruminococcaceae_UCG_010, Ruminococcaceae_NK4A214_group, and Elusimicrobium significantly decreased, adjusting the relationship between the flora toward cooperation. High-fiber-energy feeds significantly increased the concentration of VFAs, significantly decreased the relative abundances of Proteobacteria, Ruminococcaceae_NK4A214_group and Rikenellaceae_RC9_gut_group, adjusted the relationship between the flora to compete, and promoted the enrichment of metabolic pathways such as "Protein Digestion and Absorption," "Nitrogen Metabolism," "Starch and Sucrose Metabolism," and "Degradation of Other Sugars."

Conclusions: Supplementary feeding of high and low fiber energy feeds reduced the pH value of rumen fluid and the richness and diversity of microorganisms in grazing sheep, reduced the relative abundance of some harmful microorganisms, affected the metabolic activities of some fiber-digesting bacteria, regulated the interaction and competition between bacteria, increased the content of volatile fatty acids (VFAs) and the relative abundance of metabolic-related microorganisms in the supplementary feeding group, and enriched the metabolic-related pathways. However, further understand the mechanism of the effect of fiber level on the rumen of sheep, it is necessary to conduct in-depth analysis using research methods such as transcriptomics, proteomics and metabolomics.