Enhancements in flavor substances, mouthfeel characteristics and collagen synthesis in the muscle of sub-adult grass carp (Ctenopharyngodon Idella): Application of a dietary lysine nutrition strategy

The growth performance, flavor substances, mouthfeel characteristics and collagen synthesis in the muscle of sub-adult grass carp (659.07 +/- 0.74 g) were investigated after 60-day feeding with graded dietary levels of lysine (6.0-17.0 g/kg diet). The results showed that optimal dietary lysine levels boosted the growth of grass carp. Proper dietary lysine levels improved muscle inosine monophosphate, free amino acids, unsaturated fatty acid content, water holding capacity, pH and shear force (hardness). The diets also decreased lactate content, and enhanced collagen content by increasing transcription, translation and post-translational modifications of type I collagen, probably via activating TGF-beta 1/Smads and PI3K/Akt/p70S6k/la ribonucleoprotein domain family member 6 (LARP6) signaling; this enhanced prolyl 4-hydroxylase (P4H) and lysyl hydroxylase (LOX) content, thereby improving the flavor and mouthfeel of muscle. In summary, this research indicated that dietary lysine could lead to the enhancement of muscle flavor substances, mouthfeel characteristics and type I collagen synthesis in sub-adult grass carp. Based on the PWG and shear force, the dietary requirements of lysine for sub-adult grass carp are 13.43 and 12.96 g/kg, respectively.