Dietary γ-Aminobutyric Acid (GABA) Promotes Growth and Resistance to Vibrio alginolyticus in Whiteleg Shrimp Litopenaeus vannamei

An 8-week feeding trial was conducted to evaluate the effects of dietary gamma-aminobutyric acid (GABA) on growth performance, immune response, and disease resistance for juvenile whiteleg shrimp, Litopenaeus vannamei. Five isonitrogenous diets were formulated by supplementing 0 (CON), 50 (GABA(50)), 100 (GABA(100)), and 300 (GABA(300)) mg of GABA and 4 g of oxytetracycline (OTC) per kilogram of diet. A total of 225 juvenile whiteleg shrimp with an initial weight of 2.97 +/- 0.06 g were randomly distributed and reared in 15 aquaria as triplicates. After 8 weeks of the feeding trial, weight gain, specific growth rate, feed efficiency, and protein efficiency ratio of shrimp fed GABA(100) were significantly higher than those of shrimp fed CON, GABA(50), and GABA(300) diets (P < 0.05). However, there were no significant differences among shrimp fed CON, GABA(50), GABA(300), and OTC diets (P > 0.05). After nine days of challenge test with Vibrio alginolyticus, the average cumulative survival rate of shrimp fed GABA(50), GABA(100), and OTC was significantly higher than that of shrimp fed GABA(300) and CON diets (P < 0.05). These results may suggest that 100 mg dietary GABA supplementation (including endogenous GABA, 175.6 mg/kg diet) per kilogram of diet could be the optimum dietary level to replace antibiotics and improve growth performance and disease resistance in whiteleg shrimp L. vannamei.