Phosphorylation levels of mechanistic target of rapamycin (mTOR) and abundance of the Ras homolog enriched in brain (Rheb)-mTOR complex in longissimus dorsi muscle of neonatal pigs fed low-protein (LP) diets supplemented with β-hydroxy-β-methylbutyrate (HMB) or leucine (Leu) or a high-protein (HP) diet. A: phosphorylation of mTOR (p-mTOR) at Ser2481 (study 1). B: phosphorylation of mTOR at Ser2481 (study 2). C: phosphorylation of mTOR at Ser2448 (study 1). D: phosphorylation of mTOR at Ser2448 (study 2). E: Rheb-mTOR complex abundance (study 1). F: Rheb-mTOR complex abundance (study 2). AU, arbitrary units; HMB4, HMB40, and HMB80, 4, 40, and 80 μmol HMB·kg body wt−1·day−1. On the blot images, white lines between bands indicate where images from the same blots were spliced to adjust sample order on the membrane for presentation. Phosphorylated forms were normalized to the total abundances of their respective proteins. Statistical analyses was performed with 1-way ANOVA followed by Tukey’s test. Values are means ± SE; n = 7–10 pigs. Means with different letters differ at P < 0.05.