ABSTRACT
Dietary GABA plays an important role in a variety of physiological functions in animals, but this has been rarely reported in fish. This study investigated the effects of dietary supplementation with GABA on growth, serum antioxidant indicators, digestive enzyme activities, intestinal morphology, and the gene expression of Nile tilapia. Diets containing three different GABA concentrations, 0 (control), 200 mg/kg (GABA200), and 500 mg/kg (GABA500), were fed to Nile tilapia (6.97 ± 0.34 g) for 56 days. The present study found that increasing dietary GABA content could increase the fish growth performance including final body weight, weight gain, specific growth rate, average daily gain, protein efficiency ratio, and feed efficiency compared to the control diet. Interestingly, the feed conversion ratio was improved by dietary GABA supplementation. The antioxidant enzyme activities against ammonia stress of fish fed the GABA diets were significantly higher than the corresponding control group throughout the 96-h ammonia exposure. Moreover, significant increases in digestive enzyme activities including protease, amylase and lipase were found in fish fed the GABA diets. Intestinal morphology analysis revealed increased heights and widths of intestinal villi as well as thickness of the intestinal muscularis in fish fed the GABA diets compared to the control diet. The supplementation of diets with GABA significantly increased the expression level of immune- and growth-related genes. The above results indicate that dietary GABA can modulate the growth, improve their immune response and antioxidant status, gut health and morphology and gene expression of Nile tilapia. Therefore, GABA is a promising feed additive for Nile tilapia aquaculture.
