LAUSR

Abstract Identification of those cattle genetics with superior feed efficiency is necessary to increase the productivity of the entire beef industry. The aim of this study was to investigate metabolites profiling in the liver and muscle to identify physiological changes in animals in the livestock system with low or high residual feed intake. Liver and muscle were collected after slaughter from Nellore males, with high and low residual feed intake (H-RFI, n = 10 and L-RFI, n = 10, respectively). Metabolites were extracted with cold methanol/water solution (4:3 v/v). Metabolomics analyses were performed by 1D 1H nuclear magnetic resonance. Metabolites were identified using Chenomx and analysed using MetaboAnalyst 4.0. The residual feed intake classification did not change most of animal performance traits; however, animals with lower residual feed intake presented greater carcass dressing, lower carcass fat deposition. Sixty-three compounds were identified in the liver and 31 in muscle. Coexpression network analysis was carried out and identified four metabolite network modules correlated with the phenotypic traits, indicating common metabolites with a variate important projection score that influences residual feed intake. Metabolites in liver samples was correlated with energy and protein metabolism and on muscle with fat metabolism. Differences on energetic metabolism, including of carbohydrate- and fat-correlated compounds, according to residual feed intake can be assessed by importance of concentration of citrate, isocitrate, glucose-6-phosphate, nicotinamide adenine dinucleotide + hydrogen and creatine phosphate (in liver) and choline, glycine, glycerol, malonate, glucose-6-phosphate and 3-hydroxybutyrate (in muscle). Moreover, differences on protein metabolism, can be assessed by importance of creatinine, glutamine, urea and creatine phosphate concentration in liver and creatinine, creatine, anserine and carnosine in muscle. Animals with low residual feed intake presented changes in energy production, represented by carbohydrate and fatty acid metabolites, and decreased carcass fat deposition and protein turnover.