Interactions of dietary vitamin C and proline on growth performance, anti-oxidative capacity and muscle quality of large yellow croaker Larimichthys crocea

A 60-day feeding trial was conducted to investigate the effect of dietary proline and vitamin C, and their interactions on growth performance, anti-oxidative capacity and muscle quality of large yellow croaker Larimichthys crocea (initial body weight: 150.83 +/- 3.81 g). Four isonitrogenous and isolipidic diets from a 2x2 factorial design were formulated with two levels of vitamin C (50 mg/kg and 150 mg/kg) and two levels of proline (0 and 0.6%), respectively. The results showed that dietary supplementation of proline significantly improved the growth performance regardless of dietary vitamin C levels (p <.05). Significant interactions between dietary vitamin C and proline were found in muscle quality (p <.05). Liquid loss and water loss of muscle significantly decreased with dietary proline supplementation at lower level of dietary vitamin C, while the pH, hardness, and contents of alkaline-soluble hydroxyproline, total collagen and pyridinium crosslink of muscle significantly increased (p <.05). Dietary supplementations of vitamin C and proline significantly increased the activity of prolyl 4-hydroxylase in muscle (p <.05), even though no significant interaction between dietary vitamin C and proline was found (p >.05). Activity of matrix metalloproteinase 2 of muscle significantly increased with dietary vitamin C supplementation regardless of dietary proline level (p <.05). Significant interactions between dietary vitamin C and proline were found in anti-oxidative capacity of muscle (p <.05). Dietary supplementation of proline significantly increased the activities of glutathione peroxidase and copper/zinc superoxide dismutase in muscle at higher level of dietary vitamin C (p <.05). The present study indicated that dietary vitamin C and proline had synergistic effects on muscle quality and anti-oxidative capacity of large yellow croaker.