Evaluation of cysteamine supplementation in red tilapia (Oreochromis sp.) diet: Serum insulin and somatostatin, IGF-1 and GLUT4 genes expression, growth performance, and robustness against stress

Abstract

The present study evaluated the effects of cysteamine supplementation on the serum insulin and somatostatin, IGF-1 and GLUT4 genes expression, growth performance and robustness against stress in red tilapia (Oreochromis sp.). This study tested five cysteamine dietary levels (quadruplicate), i.e. treatments consisted of control (N = 0 g/kg of cysteamine), A1 (0.25 g/kg cysteamine), A2 (0.50 g/kg of cysteamine), A3 (0.75 g/kg of cysteamine) and A4 (1.00 g/kg of cysteamine). All male red tilapia juvenile, with an average body weight of 6.98 ± 0.06 g, were kept in an aquarium (100 cm × 50 cm × 50 cm) previously filled with 175 L filtered water at the density of 12 fish/aquarium. Experimental diet was fed to the fish to satiation 3 times a day for 56 days rearing period. Stress challenge test was carried out by using air exposure technique. The results showed that final body weight, feed conversion ratio (FCR), protein retention and muscle protein significantly increased (P < .05) in response to cysteamine supplementation. Polynomial orthogonal contrast analysis demonstrated that the quadratic model regression of cysteamine supplementation level for specific growth rate (SGR) is y = 58.67 × 2 + 6.9317× + 3.7973 (P = .01) with an optimum level of 0.59 g/kg of cysteamine in the diet. Optimum cysteamine supplementation resulted in reduced blood glucose, protein and triglyceride blood levels (P < .05), indicating non protein energy utilization. Plasma somatostatin levels decreased along with the increase of cysteamine supplementation. IGF-1 and Glut4 genes expression in the liver significantly upregulated (P < .05) with cysteamine supplementation. In addition, cysteamine supplementation improved the fish robustness against stress, as indicated by increased superoxide dismutase (SOD), higher post-challenge survival and lower plasma cortisol, malondialdehyde (MDA) and glucose levels (P < .05). In conclusion, optimum cysteamine supplementation (0.59 g/kg) improved growth performance and robustness against stress in red tilapia.