Effect of γ‐aminobutyric acid supplementation on growth performance,endocrine hormone and stress tolerance of juvenile Pacific white shrimp,Litopenaeus vannamei,fed low fishmeal diet

An 8‐week feeding trial was conducted to evaluate the optimum dietary γ‐aminobutyric acid (GABA) level in low fishmeal diet for juvenile Pacific white shrimp, Litopenaeus vannamei. Six practical diets (449 g kg^?1 protein, 87 g kg^?1 lipid) supplemented with graded levels of GABA (0, 50, 100, 150, 200, 250 mg kg^?1) were formulated. Each diet was randomly assigned to triplicate groups of 30 shrimps (approximately 0.44 g), and the shrimps were fed four times a day to apparent satiation. Weight gain and gain rate were significantly increased with the supplementation of GABA (P < 0.05). Hepatosomatic index and survival were also significantly influenced by the dietary GABA levels (P < 0.05) and show a similar trend to those of growth performance. Insulin and neuropeptide Y concentrations in blood were increased with the supplementation of GABA. In total, 150 mg GABA kg^?1‐supplemented diets significantly increased the survival after 12, 24 and 36 h of NH₃ stress, also increased the total antioxidant capacity, total superoxide dismutase, catalase, antihydroxyl radical and phenoloxidase activities before and after the 36 h NH₃ stress compared to basic group. These results clearly indicated that GABA could improve growth performance, antioxidative capacity and resistance against NH₃ stress in L. vannamei, and 150 mg kg^?1 GABA supplementation was suitable for L. vannamei fed with low fishmeal diet.