Substituição de fontes de proteína animal pelo concentrado proteico de soja para juvenis de tilápia-do-nilo

Abstract

Soy protein concentrate (SPC) was evaluated as a dietary replacement of animal protein sources (fish meal and poultry by-product meal) (APS) for juvenile Nile tilapia (Oreochromis niloticus). Apparent digestibility coefficients (ADC) of crude protein (CP) and dry matter (DM) were evaluated by feeding tilapia an experimental diet composed of 69.5% reference diet, 30% SPC, and 0.5% chromic oxide as inert marker. Apparent digestibility coefficients were 96.57% for CP and 76.84% for DM. In a feeding trial, increasing levels of dietary SPC (0, 33, 67, and 100%) replaced APS and were fed to tilapia juveniles (10.0 ± 0.18 g) for 60 days. Daily weight gain, specific growth rate, protein retention, feed conversion, body composition and liver histology were not significantly (P>0.05) affected by protein replacement. A second feeding trial compared tilapia’s growth performance when SPC was supplemented with methionine and threonine (100% SPC+aa, 100% SPC, and 0% SPC) as well as CP and DM digestibility. The amino acid supplementation of SPC significantly increased tilapia daily weight gain. Diets containing 100%SPC and 100% SPC+aa promoted higher protein ADC values than diet containing only APS. However, DM ADC values were significantly higher in fish fed 0% SPC when compared to 100% SPC. Therefore, SPC can replace poultry by-product meal and fish meal in diets for Nile tilapia without compromising growth performance, protein retention, body composition, liver histology, and protein digestibility. However, SPC supplementation with limiting amino acids, such as methionine and threonine, is advisable since it further increases weight gain and protein digestibility.