Interactive effects of dietary isoleucine and valine ratios to lysine in response to varying leucine to lysine ratios on Pectoralis major protein expression in commercial broilers

Abstract

The branched-chain amino acid (BCAA) consists of valine, leucine and isoleucine. The optimum ratio for each of the 3 BCAA is still unknown. Inadequate concentrations have been related to generate interactions among each other. Therefore, optimizing concentrations of dietary BCAA could improve broiler growth performance and carcass yields. Therefore, a central composite design (CCD) experiment was performed to understand the impact of dietary BCAA concentrations on Pectoralis major (PM) muscle protein expression to evaluate the mechanisms that determine how BCAA ratios affect broiler growth and muscle deposition. For this, a total of 2,592 d-old Ross 344 × 708 male broilers were placed randomly in 144 floor pens. A 23 CCD determined each pen to receive 1 of 15 dietary treatments from 20 to 35 d of age, varying in digestible valine:lysine (Val:Lys; 64 to 87), leucine:lysine (Leu:Lys; 110 to 185), and isoleucine:lysine (Ile:Lys; 52 to 75). During d 35, 1 bird per pen was randomy selected, a PM sample was collected, and protein extraction was performed. A proteomic analysis via data independent acquisition protein sequencing with a timsTOF Pro 2 LC/MS/MS and Spectronaut 15 software analysis was performed. Branched-chain-amino-acid aminotransferase (BCAT1), adipocyte-type fatty acid-binding protein (FABP4), phosphoserine aminotransferase (PSAT1), O-N-acetylglucosamine transferase subunit p110 (OGT), large neutral amino acids transporter small subunit 1 (SLC7A5), ribosomal protein S6 kinase (RPS6KA3), eukaryotic elongation factor 2 (EEF2), eukaryotic translation initiation factor 4B (EIF4B), eukaryotic translation initiation factor 4E (EIF4E), CAP-Glycine domain containing linker protein 1 (CLIP1), mitogen-activated protein kinase 3 (MAPK3), Protein kinase domain-containing protein (MAP2K1), Dual-specificity mitogen-activated protein kinase kinase 2 (MAP2K2), paxillin (PXN), and ragulator complex protein (LAMTOR3) were identified, quantified, and analyzed with significance set at P ≤ 0.10 as a CCD utilizing the RSREG procedure of SAS ver. 9.4. PSAT1 protein expression model was significant (P = 0.0149; R2 = 0.24), while the models for the other proteins were not significant (P ≥ 0.9592; R2 values ≤ 0.0336). For PSAT1 protein expression a linear model effect (P = 0.0023) was observed. However, no linear (P ≥ 0.5223), quadratic (P ≥ 0.2085) or cross product (P ≥ 0.5886) regression effects were observed for any other protein. Interestingly, minimum stationary pointes were observed for BCAT1, RPS6KA3, eEF2, MAPK3, and LAMTOR3 proteins. Overall, due to stationary saddle points, optimal values for the proteins could not be obtained. Although, the coefficients for the isoleucine to lysine Ile:Lys cross-product ratio effect on PSAT1 protein expression was significant (P = 0.0957). Overall, results presented herein indicate that protein expression on proteins related to broiler skeletal muscle growth may not be impacted due to varying concentrations of dietary BCAA. However, further exploration will be required to understand what mechanisms are influenced by BCAA to lysine ratios on growth and muscle development.