Dietary valine requirement of juvenile red sea bream Pagrus major

• Dietary valine requirement was determined for juvenile red sea bream.
• Fish growth performance was significantly affected by valine levels.
• Innate immunity of fish was improved by increment of valine level.
• Lower postprandial ammonia levels were obtained at valine levels of 1.69 and 2.04%.
• Valine requirement of juvenile red sea bream was estimated to be 0.9% of dry diet.

A 12-week feeding trial was conducted to determine dietary valine requirement of juvenile red sea bream (Pagrus major). Six isonitrogenous (45% crude protein) and isocaloric (4.38 kcal g− 1 gross energy) semi-purified diets were formulated with graded levels of valine (0.27, 0.79, 1.22, 1.69, 2.04 and 2.38% dry diet). Triplicate groups of fish (32.04 ± 0.2 g) were fed one of the diets to apparent satiation twice daily. At the end of the feeding trial, significantly (P < 0.05) higher growth performance and feed utilization were obtained at dietary valine levels of ≥ 0.79% compared to fish fed 0.27% valine. Significantly lower whole-body moisture and higher protein contents were recorded at over 0.79% valine level and lipid content increased in fish fed 2.04% valine. Non-specific immune responses of fish were significantly improved by increment of dietary valine up to 2.04%. Plasma total protein, aspartate aminotransferase and total cholesterol levels were significantly affected by valine levels. Significantly lower postprandial ammonia excretion levels were obtained in fish fed dietary valine levels of 1.69 and 2.04% compared to the fish offered 0.27% valine. The optimum dietary valine requirement level was estimated at approximately 0.9% of dry diet (2% of dietary protein) by a broken-line regression analysis on the basis of weight gain and protein deposition.