Network pathway differential expression muscle protein in Nelore cattle classified to low and higher RFI

The variations in residual feed intake (RFI) occur by several metabolic factors in animals. The main physiological mechanisms that influence variation in the RFI are related to maintenance requirements, ion transport, response to stress, tissue metabolism and heat increment. The objective was to evaluate biological pathway of proteins differentially expressed in Longissumus dorsi muscle in high and low RFI Nellore animals. To investigate the effects of feed efficiency on Longissimus dorsi, proteomic analysis was performed using 2-dimensional difference gel electrophoresis followed by mass spectrometry using MALDI TOF/TOF. Proteins were identified from their peptide sequences, using Mascot program. Categorical annotation was supplied in the form of Gene Ontology (GO) to Biological Process (BP), Molecular Function (MF) and pathway. To visualization of network was used Cytoscape software using Cluego plug-in to integrate protein networks. The Fisher's test was used to calculate a P-value determining the probability that each biological function assigned to that data set was relevant. A P-value < 0.05 indicated that the function was significant to the data set. Animals classified low RFI showed differences of 3.31 kg DMI / day, and higher values for feed efficiency variables feed efficiency (FE) 35% and total feed efficiency (TFE) 12% and 21% reduction in feed conversion as compared to animals rated to high RFI. Differences were observed in the expression of proteins related to the muscle tissue of cattle classified for high and low RFI. The myosin light chain expression (1 MYL1) in animals classified low RFI was about 3.34 times higher compared to the animals of high RFI. Selected phenotypes low RFI presented relation with genes associated with the development of muscle fiber, muscle function and organization of the cytoskeleton. Protein expressions and enrichment analysis indicate that the phenotype classified to RFI exhibited differential expression of proteins with functions associated with signal transduction pathways, anabolic activities energy-sensing and energy coordination activities. In contrast, the low RFI cattle phenotype exhibited upregulation of protein MYL1 which are associated with actin-myosin filaments, cytoskeletal architecture, and presented muscle fibers and stress-related or stress-responsive genes. The enrichment analysis the RFI phenotype presented linkage with proteins related oxidative stress, presenting interaction with gene that is modulated by oxidative stress.