EFFECTS OF DIETARY SUPPLEMENTATION OF DL-METHIONINE ON THE GROWTH PERFORMANCES, MUSCLE GROWTH-RELATED GENE EXPRESSION AND HAEMATO-BIOCHEMICAL RESPONSES OF GIFT TILAPIA

Nutrigenomics provides a genetic understanding of common dietary nutrients affecting muscle growth by altering the expression or structure of an individual's genetic makeup and this approach is gaining understanding of genomic responses in fish nutrition. Methionine is an indispensable amino acid that plays an important role in fish health. The studies on muscle-growth-related gene expression in GIFT tilapia in response to dietary methionine supplementation has not been reported. The present study was conducted to study the effects of dietary DL-methionine supplementation on the growth performances, muscle-growth-related gene expression, haematological and biochemical responses of GIFT tilapia.

A 60-day indoor feeding trial was conducted in 15 nos. of 1 X 1 X 1.5 m sized cages in triplicate, with GIFT tilapia weighing on an average of 10 g. Five corn-soy based isonitrogenous and isoenergetic experimental diets (32% crude protein) were formulated with graded levels of methionine (% of dry diet) viz., T0 (0.75), T1 (0.9), T2 (1.05), T3 (1.2) and T4 (1.35 %). This feeding trial was conducted in 15 nos. of 1 X 1 X 1.5 m sized cages in triplicate. Among the experimental diets T1, diet containing methionine level of 0.9 % of dry diet yielded significantly (p<0.05), higher mean body weight gain (51.56±0.23 g) followed by T0 (45.2±0.49 g), T2 (42.58±0.10 g), T3 (37.33±0.06 g) and T4 (30.87±0.13g). The best results in terms of feed conversion ratio (1.12±0.08), specific growth rate (1.76±0.01), feed efficiency ratio (0.89±0.06), average daily growth (1.14±0.05), haemato-biochemical parameters and muscle-growth-related gene expressions were observed in T1. The results demonstrated that the dietary methionine requirement in corn-soy based diet for GIFT tilapia would be 0.9 % of dry diet for better growth performances.