The aim of this study was to investigate the use of corn distillers dried grains with solubles (DDGS) (27.11% CP) and Foots (20.84% CP) as corn processing by-products in monosex Nile tilapia, Oreochromis niloticus diets to replace yellow corn as an energy source and its effect on growth performance, nutrients utilization, whole body proximate composition, nutrients digestibility and economic efficiency. Three hundreds and seventy five fingerlings of Nile tilapia (10± 0.05 g) were randomly distributed into 15 circular plastic tanks (1000 L), representing 5 treatments. Isonitrogenous (25 to 25.84%) and isocaloric (4174.79 to 4364.65 Kcal GE/kg) experimental diets were prepared with substitution levels of DDGS 0% (T1), 20% (T2) and 40% (T3) and Foots 20% (T4) and 40% (T5). The experimental period lasted for 18 week. Results showed that both of DDGS and Foots have higher in all measured amino acids content than those in yellow corn except cysteine. Moreover, DDGS and Foots have higher content of linoleic, oleic, stearic and palmitic acids than those in yellow corn. Also DDGS and Foots covered the nutrient requirements of the essential fatty acid linoleic (18:2 ω 6) for Nile tilapia. Feed intake was significantly decreased as corn partially replaced by Foots more than the DDGS. Apparent digestibility coefficient of CP, EE, NFE and energy recorded the highest values for the T4 (75.76, 89.86%, 57.48 and 68.71%), respectively, followed by T3 with significant differences.
The increasing in substitution levels of yellow corn by DDGS did not significantly (P˃0.05) had an effect on Nile tilapia performances. However weight gain and specific growth rate SGR were gradually decreased with increasing the substitution levels of Foots. The CP content of Nile tilapia carcass was significantly increased with increasing the substitution levels of DDGS (T3) and Foots (T5). Feed conversion ratio (FCR) of the fish fed diets T4 (20% Foots) was the best followed by T5 (40% Foots). The cheaper feed cost gain was obtained from T5(40% Foots) followed by T4(20% Foots).