Both n-6 and n-3 fatty acids are required for maximal growth of juvenile hybrid tilapia

An 8-week feeding experiment was conducted to provide preliminary informati on on essential fatty acid requirements of hybrid tilapia (female Nile tila pia Oreochromis niloticus x male blue tilapia O. aureus). Seven semipurifie d diets containing 30% crude protein from casein with 3.2 kcal available en ergy/g were supplemented with 5% of either lard (L), corn oil (C), cod live r 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 oi l(1:1:1, L-C-F). Each diet was fed to three replicate groups of fish initia lly weighing 0.84 +/- 0.02 g (mean +/- SD) in 60-L aquaria connected as a c losed recirculating-water system containing freshwater at 25 +/- 1 degrees 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, LF or C-E Protein deposition was significa ntly better in fish fed GC-F than in fish fed L-E Fatty acid compositions o f 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 f atty acid are essential for maximum growth of juvenile hybrid tilapia.