Using distillers dried grains as an alternative protein source in Nile tilapia (Oreochromis niloticus) feeds

This work was conducted in the regional laboratory for food and feed, Agriculture Research Center, Giza, Egypt, in a closed recirculation water system for 12 weeks to determine the effect of replacing 0, 10, 20, 30 and 40% soybean meal and yellow corn in tilapia (Oreochromis niloticus) diets by Distillers Dried Grains (DDGS) with and without enzyme (Ameco Zyme 2x, 0.25g/kg). Therefore, nine isonitrogenous (30% CP) and isocaloric (3200 kcal GE/kg) experimental diets were formulated, D1, repsant the (control). In the other experimental diets, soybean meal and yellow corn mixture was replaced with DDGS at a rate of 10% (D2), 20% (D3), 30% (D4), 40% (D5), 10% DDGS+ Enzyme (D6), 20% DDGS+Enzyme (D7), 30% DDGS+ Enzyme (D8) and 40% DDGS+ Enzyme (D9). A total number of 405 tilapia fry (0.98 g±0.01) were randomly distributed into 27 tanks (60 liters each) at a stocking rate of 15 fry/tank. After 84 days from the experiment start no significant differences (P 0.05) were observed in survival rate, the highest specific growth rate (3.5 %/day) was recorded for fish feed D7, while fish fed D5 showed the lowest value (2.83 %/ day). The best feed conversion ratio (FCR) was occurred when fish fed D6 or D7 while the worst value was recorded by fish group fed D5. Protein efficiency ratios (PER) were found to be high when fish were fed diets containing enzyme. Body crude protein content for fish fed D1, D2, D6 or D7 were significantly higher than the other diets while fish group fed D5 showed the highest significant (P 0.05) body fat content compared to fish fed the other diets. The obtained results refers to the possibilities of replacing soybean meal and yellow corn mixture in the control diets with DDGS up to 20% without enzyme and up to 30% with enzyme addition.