Both n-6 and n-3 Fatty Acids Are Required for Maximal Growth of Juvenile Hybrid Tilapia

Abstract

An 8-week feeding experiment was conducted to provide preliminary information on essential fatty acid requirements of hybrid tilapia (female Nile tilapia Oreochromis niloticus × male blue tilapia O. aureus). Seven semipurified diets containing 30% crude protein from casein with 3.2 kcal available energy/g were supplemented with 5% of either lard (L), corn oil (C), cod liver oil (F), lard and corn oil (1:1, L–C), lard and cod liver oil (1:1, L–F), corn oil and cod liver oil (1:1, C–F), or lard, corn oil, and cod liver oil (1:1:1, L–C–F). Each diet was fed to three replicate groups of fish initially weighing 0.84 ± 0.02 g (mean ± SD) in 60-L aquaria connected as a closed recirculating-water system containing freshwater at 25 ± 1°C. Results indicate that significantly (P < 0.05) higher weight gain, feed efficiency (FE), protein efficiency ratio (PER), and protein deposition (PD) were associated with fish fed the diet supplemented with F. Among groups fed diets containing F, weight gain was significantly higher in fish fed L–C–F than in fish fed L–F and F. Fish fed L–C–F had significantly higher FE and PER values than those fed F, L–F or C–F. Protein deposition was significantly better in fish fed L–C–F than in fish fed L–F. Fatty acid compositions of liver and muscle in fish generally reflected the composition of the diet. These data suggest that n-3 highly unsaturated fatty acid as well as n-6 fatty acid are essential for maximum growth of juvenile hybrid tilapia.