Effect of replacing fishmeal and oil with simple or complex mixtures of vegetable ingredients in diets fed to Nile tilapia (Oreochromis niloticus)

The effect of replacing fishmeal with simple or complex mixtures of plant proteins in tilapia diets was examined. Diet formulations were arranged in a 2 x 4 factorial design with two types of plant protein mixtures used to replace fishmeal (simple: soybean meal and maize gluten meal or complex: soybean meal, maize gluten meal, dehulled flax, pea protein concentrate and canola protein concentrate) and four levels of protein originating from fishmeal (1000 g kg(-1), 670 g kg(-1), 330 g kg(-1) and 0 g kg(-1)). Diets contained equal digestible protein (380 g kg(-1)) and digestible energy (17.6 MJ kg(-1)). The average daily gains, specific growth rates and feed efficiencies of fish fed diets with 0 g kg(-1) fishmeal were significantly lower than fish fed diets with the 330 g kg(-1), 670 g kg(-1) or 1000 g kg(-1) fishmeal levels. Fish fed the complex diets had significantly higher average daily gains, specific growth rates, feed : gain ratios and protein efficiency ratios than those fed the simple diets. Intestinal villus length decreased with decreasing levels of fishmeal and increased with increased diet complexity but the effects were not significant. Replacement of fishmeal with a complex mixture of plant ingredients may allow a greater replacement of fishmeal in diets fed to Nile tilapia.