To investigate the effects of low net energy (NE) diets on the meat quality of Tunchang pigs, a total of 96 Tunchang pigs at 55 days of age and with an initial body weight of 26.42 ± 1.04 kg were randomly assigned to four treatment groups with NE levels of 9.82 (control group, CG), 9.57 (EY1), 9.32 (EY2), and 9.07 MJ/kg (EY3). Each treatment consisted of 6 replicates with 4 pigs per replicate. The trial lasted for 63 days. The results showed that dietary NE levels had no significant effects on average daily gain or feed conversion ratio ( P > 0.05), whereas the average daily feed intake was significantly higher in the EY3 group than other groups ( P = 0.018). Compared with CG group, pigs in the EY3 group exhibited higher shear force ( P = 0.008) and lower intramuscular fat (IMF) content ( P = 0.046) in the longissimus dorsi muscle. In addition, low NE diets increased muscle fiber diameter, cross-sectional area, and relative mRNA expression of MYHC IIb ( P < 0.05), while reducing the relative mRNA expression of MYHC I and MYHC IIa ( P < 0.05). Proteomic analysis indicated that low-NE diets modulated key cytoskeletal proteins in muscle cells, including myosin-binding protein C slow type, myosin regulatory light chain 3, troponin C slow type, myosin heavy chain 2, and cysteine and glycine-rich protein 3, thereby promoting a shift from oxidative to glycolytic muscle fibers. Metabolomic results further confirmed this fiber-type transition, showing an accumulation of glycolytic metabolites, depletion of tricarboxylic acid cycle intermediates, and reduced biosynthesis of unsaturated fatty acid metabolites. Overall, reducing dietary NE to 9.32 MJ/kg had no adverse effects on growth performance or meat quality of Tunchang pigs; however, a further reduction to 9.07 MJ/kg induced glycolytic fiber remodeling, increased muscle fiber diameter and cross-sectional area, and decreased IMF deposition, ultimately impairing meat tenderness.
Wu et al. (2026) studied this question.