Effects of dietary thiamin on flesh quality in grass carp (Ctenopharyngodon idella)

An 8 week experiment was conducted to assess the effect of dietary thiamin on meat quality of grass carp. Totally, 540 fish were randomly distributed into 18 cages (1.4 m x 1.4 m x 1.4 m) each containing 30 fish in three replicates. Test fish were fed with respective diets for four times daily: 0.12 (thiamin un-supplemented diet), 0.43, 0.83, 1.25, 1.62 and 2.04 mg thiamin/kg diet. Results revealed that optimum dietary thiamin improves grass carp flesh quality in five aspects: (1) increased nutritional quality (fillet protein, lipid contents) was associated with increasing target of rapamycin and casein kinase 2 expression, (2) improved flesh flavour via increasing the flavour amino acids contents (Glu, Asp, Gly, Ala, Leu and Ile), (3) elevated fillet healthcare components contents (especially docosahexaenoic acid and eicosapentaenoic acid contents), (4) improved sensory characteristics (pH, firmness, water-holding capacity) of flesh and (5) enhanced flesh antioxidative capacity by elevating the activities and expression of antioxidant enzymes, which was involved in elevating Nrf2 expression and down-regulating Keap1a and Keap1b expression. Dietary thiamin affected fish flesh quality correlated with changes in muscle flavour, healthcare components, sensory characteristics, antioxidant capacity, target of rapamycin and Nrf2 expression.