Effects of dietary γ‐aminobutyric acid levels on the growth, serum biochemical indexes, immune‐related signalling molecules of Jian carp

Abstract

In order to evaluate the protect effects of γ-aminobutyric acid (GABA) on the growth, serum biochemical indexes, immune-related signalling molecules of Jian carp (Cyprinus carpio var. Jian), fish were randomly divided into 6 groups, which fed six diets with different GABA levels (0, 30, 60, 90, 120 and 150 mg/kg) for 8 weeks, respectively. The results indicated the following: body weight gain, specific growth rate, feed intake, feed efficiency ratio and protein efficiency ratio were significantly improved by dietary GABA supplementation, the levels of total protein, albumin, glucose and the activity of superoxide dismutase in serum responded same trend; whereas, the activities of aspartate aminotransferase, alanine aminotransferase and malondialdehyde contents were opposite. Moreover, the activities of lysozyme and alkaline phosphatase and the content of nitric oxide in head kidney and spleen showed significantly increased under GABA pre-supplementation. Furthermore, GABA pre-supplementation had significantly higher expressions of interleukin-2, interleukin 10, interferon γ and lower expressions of nuclear factor-kappa B, interleukin-1β, tumour necrosis factor α in head kidney and spleen when compared to the control group. These results indicated that GABA pre-supplementation improved the growth in Jian carp, which could be related to the activation of serum biochemical indexes and immune-related signalling molecules, showing the potential of GABA as a novel feed additive to prevent stress. The recommendation dietary GABA level for Jian carp, estimated by quadratic regression analysis based on BWG and FER, was 99.01 mg/kg and 96.75 mg/kg, respectively.