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 gamma-aminobutyric acid (GABA) level in low fish-meal 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 fish-meal diet.