INFLUENCE OF DIETARY-PROTEIN INTAKE AND RECOMBINANT HUMAN SOMATOTROPIN ADMINISTRATION ON GROWTH AND BODY-COMPOSITION OF JUVENILE TAMBACU (APIARACTUS-MESOPOTAMICUS X COLOSSOMA-MACROPOMUM CROSS)

This experiment was undertaken to study the interaction between level of dietary protein and recombinant human somatotropin (rhGH) administr ation on performance and body composition of juvenile tambacu (a cross bred Brazilian fish). A total of 72 juvenile tambacu, initially weighi ng and measuring (mean +/- s.e.m.) 23 +/- 2 g and 9 +/- 0.5 cm, respec tively, were randomly divided into 18 groups of 4 fish each. Water tem perature was 28 degrees C. Triplicate groups received one of two level s of dietary protein (15 and 30% as fed basis) and one of 3 doses of r hGH (0, 2 and 4 mu g/g) via intraperitoneal injection twice a week for 6 weeks, using a randomized complete block design. Somatotropin was n oted to stimulate linear and body weight gain. The higher protein leve l supported increased growth in weight and length, but there was no in teraction between protein level and rhGH dose for either parameter. Pr otein efficiency ratio and percentage protein deposited showed higher values on diets containing 15% protein. Somatotropin treatment did not significantly affect body composition, but there was a trend towards improved protein retention and reduced carcass lipid. In conclusion, t he results of this experiment suggest that rhGH is able to stimulate l inear gain in tambacu.