Effects of Four Vegetable Protein Supplementation on Growth, Digestive Enzyme Activities, and Liver Functions of Juvenile Tilapia, Oreochromis niloticus×Oreochromis aureus

Four isonitrogenous (gross protein content 30%) and isoenergetic (gross energy content 15 kJ/g) diets were formulated to investigate the effects of inclusion of plant proteins on the hybrid tilapia (Oreochromis niloticus×Oreochromis aureus). The plant proteins tested were soybean meal (SBM), rapeseed meal (RSM), cottonseed meal (CSM), and peanut meal (PNM). In each diet, 30% of the protein was supplied by fish meal, and the rest of protein was supplied by the plant protein tested. Each diet was randomly fed to three groups of hybrid tilapia for 8 wk in a recirculating freshwater system. The results showed that the best performance in terms of final weight, specific growth rate, feed efficiency ratio, and protein efficiency ratio were shown in diets SBM and CSM. Four parameters were significantly affected by dietary RSM (P 0.05). The highest activities of glutamate-pyruvate transaminase, glutamate-oxaloacetate transaminase, and superoxide dismutase in the liver were observed in group SBM and the poorest in group RSM. The results show that 39% CSM may be included in the practical diets without inhibiting fish performance. Although the inclusion of 50% RSM resulted in significantly lower growth performance, it produced histopathological damage in the liver.