Maternal dietary protein induces opposite myofiber type transition in Meishan pigs at weaning and finishing stages

To describe the effects of maternal dietary protein level on offspring skeletal muscle fiber plasticity, 14 Meishan sows were fed on either low-protein (LP) or high-protein (HP) diets throughout gestation and lactation, and the myofiber characteristics of the offspring were observed both at weaning and finishing. Body weight, as well as the longissimus dorsi (LD) and psoas major (PM) muscle weights were significantly higher (P < 0.05) in HP piglets at weaning with increased myofiber cross-sectional area and higher expression of myosin heavy chain (MyHC) IIb mRNA and MyHC II protein in LD and IIx mRNA in PM. A conversed transition towards higher proportion of type I fibers in LD, together with decreased MyHC II protein and MyHC IIb mRNA in both LD and PM, was observed at finishing stage in HP group. Although the slaughter weight and meat quality were not affected, the fast-to-slow shift in myofiber types was detected at slaughter.