IMPACT OF ALTERING DIETARY OMEG 6 TO OMEGA 3 FATTY ACIDS RATIO ON GROWTH PERFORMANCE, CARCASS COMPOSITION, HEMATO-BIOCHEMICAL PARAMETERS AND ABSORPTIVE CAPACITY OF THE INTESTINE OF NILE TILAPIA

The present study investigated the influence of altering omega 6 to omega 3 fatty acids (FA) ratio on growth, hemato- biochemical parameters and absorptive capacity of Nile tilapia. One hundred and fifty fingerlings (25.1±0.3 g), were assigned into 3 groups (5 replicates each) and fed on iso-caloric and iso-nitrogenous diets. Diets were supplemented with fish and soy oil to create 3 different ratio of omega 6 to omega 3 FA, namely, 0.91, 2.85 and 9.3 parts of omega 6 to 1 part of omega 3 (R1, R3 and R9, respectively). Increasing the ratio from R1 to R9 significantly decreased average daily gain and increased feed conversion ratio. Also this alteration decreased ash content in the carcass on the expense of ether extract. Number of erythrocytes, packed cell volume, hemoglobin concentration were significantly increased in fish fed R1. Feeding R9 increased heterophils and decreased lymphocytes as compared with R1 and R3. Fish fed R1 significantly had high serum protein and serum antibacterial activity (47.6%) than R9 (43.5%) and R3 (44.9%). Feeding R1 significantly decreased serum triglycerides, cholesterol and creatinine. Feeding R3 and R1 enhanced absorptive capacity of jejunum villi more than the group fed R9. Increasing the ratio of omega 6 to omega 3 FA from R1 to R9 decreased growth performance through decreasing absorptive capacity of jejunum villi. However, Feeding R3 had a positive effect on growth performance and absorptive capacity of the intestine of Nile tilapia. Key words : fish oil; growth performance; intestinal villi; Nile tilapia; soybean oil