Comparing the Effects of Feeding a Fish Oil- or a Cod Liver Oil -Based Diet on Growth, Feed Utilization and Muscle Fatty Acid Composition Nile Tilapia (Oreochromis niloticus)

The present study was performed to investigate the influence of fish oil (FO) and cod liver oil (CLO) as the dietary lipid sources on the growth performance, feed utilization and fatty acid (FA) composition of Oreochromis niloticus. two isonitrogenous (38% crude protein), isocaloric (18.9 MJ GE/kg) diets containing 6% of added fat from the lipid sources were formulated and used. Each diet was fed to triplicate groups of 17 fish of 18.18 ± 0.02 g mean initial body weight fed with %3 body weight two times a daily. The tilapia was raised at 28±1 °C in 6 square experimental cages (1×1×1.25 m) during the 60 days. Results showed that the source of added lipid significantly influence (P<0.05) final body weight, live body weight and daily growth rate but did not affect specific growth rate, feed conversion ratio and survival, rate of tilapia. There was no significant difference in the fillet proximate composition of fish fed the FO or CLO diets, except for fish fed the CLO diet showed lower lipid deposition (P<0.05). The deposition of fatty acids in fish tissues was generally influenced by the fatty acid profile of the diets. Fillet fatty acid profiles of tilapia fed CLO-based diet had significantly higher concentrations of saturated and monounsaturated fatty acids, but lower levels of polyunsaturated fatty acids (PUFA) compared to the fish fed the FO diet. Fillet of fish fed the FO diet had significantly higher concentrations of DHA (docosahexaenoic acid) compared with fish fed CLO-based diets (P<0.05). EPA (eicosapentaenoic acid) did not showed significantly different both diet (P>0.05). In fish fed FO diet group, both n−3 and n−6 PUFA were the highest when compared with fish fed with CLO diet. The lipid source not influenced (P<0.05) hepatosomatic index (HSI) and viscerosomatic index (VSI). However, fish fed CLO contained diet showed significantly higher liver fat (20.20±0.22) than fish fed FO diet group (13.88±0.22) (P<0.001).