Feed Restriction in Angus Steers Impacts Ruminal Bacteria, Its Metabolites, and Causes Epithelial Inflammation

Abstract

We identified alterations in the ruminal microbiome, metabolome, and epithelial inflammatory response due to moderate feed restriction (FR). Ruminal digesta and epithelial biopsies from seven ruminally cannulated Angus steers were initially collected during ad libitum access to feed (PRE). After a 10 day recovery, steers underwent a 3-day FR period (FRP) at 25% intake of PRE followed by a 15 day recovery (POST) phase with ad libitum access to feed. At the end of FRP and POST, ruminal digesta and epithelial biopsies were collected again for microbial DNA and tissue RNA extraction. RT-qPCR was applied for relative microbial abundance and RNA extraction. Metabolite profiling of digesta was performed via GC-MS. The abundance of Succinivibrio dextrinosolvens, Streptococcus bovis, and Bifidobacteria spp. (N124) was higher (p < 0.05) during FRP than PRE and POST, while Lactobacillus spp. (C25), Escherichia coli (EC42405), Fibrobacter succinogenes, and Megaspheara elsdenii abundances were lower in FRP than PRE (p < 0.05). The TNF and TLR2 mRNA abundance was greater in FRP than PRE (p < 0.05). Among 15 detected amino acids, glutamine, isoleucine, lysine, phenylalanine, threonine, and valine were lower (p < 0.05) in FRP than PRE. Metabolite pathway analysis revealed alterations in amino acid, fatty acid, vitamin, and energy metabolism during FRP (p < 0.05). The mRNA of the proinflammatory genes TNF and TLR2 in the epithelium peaked (p < 0.05) at FRP and remained higher at POST. Results indicated that a short FR influenced ruminal bacteria, reduced concentrations of most metabolites, and triggered an inflammatory response.