Determination of optimal dietary valine concentrations for improved growth performance and innate immunity of juvenile Pacific white shrimp Litopenaeus vannamei

A study was conducted to evaluate dietary valine (Val) requirement for Pacific white shrimp ( Litopenaeus vannamei ). Five isonitrogenous (353 g/kg) and isocaloric (4.08 kcal/g) semi-purified diets containing graded levels of Val (3, 6, 9, 12 or 15 g/kg) were formulated. Quadruplicate groups of 12 shrimp (average body weight: 0.46 ± 0.00 g) were fed one of the experimental diets (2–5% of total body weight) for 11 weeks. Maximum weight gain was observed in 9 g/kg Val group. However, the growth performance was reduced when Val concentration in diets were higher than 12 g/kg. Shrimp fed the diets containing 3 g/kg Val showed significantly lower protein efficiency ratio, whole-body crude protein and Val concentrations. Dietary inclusion of Val significantly improved the relative expression of insulin-like growth factor binding protein and immune-related genes (prophenoloxidase, lysozyme and crustin) in the hepatopancreas and 9 g/kg Val group showed highest expression among all the groups. Polynomial regression analysis revealed that diet for juvenile L. vannamei requires to contain approximately 9.5 g/kg of Val (27 g/kg based on protein level) to ensure optimal growth and improving overall health.