Effect of dietary gamma-aminobutyric acid on growth performance, haemato-immunological responses, antioxidant enzymes activity, ghrelin and IGF-I expression of Labeo rohita (Hamilton, 1822) fingerlings.

Abstract

Gamma-aminobutyric acid (GABA) is a four-carbon neurotransmitter and plays a major role in an increasing feed intake and nutrient utilization in aquatic animal. GABA used as a feed additive to determine its effect on Labeo rohita fingerlings growth, haemato-immunological status, antioxidant enzymes activity and expression of ghrelin and IGF-I gene. A 60-day experiment was conducted to test five isonitrogenous (CP 35%), isolipidic (CL 6%) and isoenergetic (383 kcal/100 g) diets with varying level of GABA viz., 0 (control), 25 (T1), 50 (T2), 75 (T3) and 100 (T4) mg/kg of GABA respectively. The 225 fingerlings with 15 fish/tank (ave.b.w. = 6.05 ± 0.20 g) were randomly distributed in five treatments with having three triplicate each following a CRD. The T3 group had significant (p < 0.05) higher WG%, SGR and PER than T2, T4, T1 and control treatment groups. However, opposite trend was observed in case of FCR. Similarly, the T3 group showed the significantly higher blood Hb, RBC, PCV, total protein, albumin and globulin content as compared to control and other treatment groups. However, WBC, A/G ratio, glucose, cortisol and whole-body composition did not affected. In comparison to the control and T1, T2 and T4 treatment groups, the SOD and catalase activity in the liver and gills were considerably reduced in the T3 group. The T3 treatment group was shown to have the highest levels of ghrelin and IGF-I mRNA expression in the brain and liver, respectively. According to second-order polynomial regression analysis, the highest SGR and expression of IGF-I were determined between 65 and 72 mg/kg inclusion level of GABA. The diet containing 68 mg/kg GABA level is therefore determined to be the best inclusion for promoting maximal growth and feed utilization in L. rohita fingerlings.