L-threonine requirement of silver catfish (<i>Rhamdia quelen</i>): growth performance, body composition, plasma and liver metabolites

A feeding trial was performed to evaluate the effects of dietary L-threonine supplementation on growth and body composition fingerlings Rhamdia quelen (initial weight: 4.47 ± 0.39 g). Five diets (370 g/kg crude protein 14.23 MJ / kg digestible energy) containing levels (16.0, 22.0, 28.0, 34.0, 40.0 g threonine/kg protein) were fed quadruplicate groups fishes for 10 weeks. The analysed variables influenced by threonine levels. Fish with diet 16.0 CP showed lower deposition nutrients. In addition unsatisfactory performance, fish subjected presented higher hepatosomatic index scores changes in concentrations some plasmatic metabolites. To determine ideal level diet, weight gain, specific rate feed conversion ratio broken-line quadratic regression. results indicate that a inadequate causes insufficient growth. Dietary requirement R. estimated between 24.5 32.5 threonine/ protein, corresponding 9.1 12.0 g/ initial silver catfish.