The aim of this study was to evaluate different levels of soybean oil inclusion in diets for Nile tilapia. 270 tilapia, with an initial weight of 425.33 ± 32.37 g and initial length of 25.53 ± 2.00 cm, were randomly distributed in 15 tanks. The diets were formulated to be isonitrogenous (30%) using five increasing levels of soybean oil (0.00; 15.00; 30.00; 45.00 and 60.00 g kg−1) with each level having three replicates. The evaluated parameters were: performance (survival, daily weight gain, feed conversion, hepatosomatic index, visceral fat, carcass yield, fillet yield and dressed out yield), hematological and biochemical blood aspects, total protein, cholesterol, glucose, triglycerides, hemoglobin, hematocrit and red blood cells, and the chemical composition of the fillets (moisture, crude protein, lipids, and ash). Quadratic effects (P < 0.05) were observed for the variables: daily weight, weight gain, final weight, carcass yield, visceral fat, and hepatosomatic index. For blood variables, a quadratic effect (P < 0.05) for total cholesterol was observed. For chemical composition analyses of the fillets, there were no effects (P > 0.05) observed with the increase of soybean oil. A total of 22 fatty acids were determined in the fillets of the tilapia fed with different soybean oil levels. Among fatty acids, the highest concentrations were for 16:0 (238.40 to 262.19 mg g−1); 18:1n-9 (215.36 to 277.61) and 18:2n-6 (LA) (157.84 to 224.49).
It is concluded that the addition of around 45.0 g kg−1 of soybean oil to the finisher diet of Nile tilapia provides better growth performance. Animals fed the diet, used the nutrients to produce recommended PUFA/SFA values. Dietary supplementation was also effective at improving the nutrition values of the meat.