Effect of conjugated linoleic and docosahexaenoic acids on growth of juvenile tilapia Oreochromis niloticus

The present study was conducted to investigate the effects of dietary conjugated linoleic acid (CLA)- and conjugated docosahexaenoic acid (CDHA)-supplemented diets on the growth and body lipid composition of tilapia Oreochromis niloticus. Four dietary treatments of linoleic acid (LA), CLA, docosahexaenoic acid (DHA) and CDHA were tested in this experiment over a feeding period of 9 weeks. The initial average body weight and length of fish were 4.53+/-0.96 g and 5.18+/-0.34 cm, respectively, and temperature was maintained at 25+/-1degreesC. Two replicate groups and two control groups of fish were applied among the four dietary treatments and each group consisted of 20 juvenile fish. Growth rate, feed efficiency and tissue lipid contents were not significantly affected (P<0.05) by CLA compared to the LA control group. A higher level of hepatosomatic index and lower growth rate were obtained from the CDHA dietary group. CLA and CDHA isomers were detected mainly in non-polar lipids of muscle, liver and brain. Lower values of mono-unsaturated fatty acids and 18:2n-6 levels were found in the CLA dietary fish group and there was no effect on the 20:4n-6 level in muscle, liver and brain. Conversely, higher levels of total mono-unsaturated fatty acids were found in liver and the 20:5n-3, 22:5n-3 level of the muscle polar fraction in the CDHA dietary fish group. These results indicate that 5% of CLA in diet does not influence the growth and feed efficiency of juvenile tilapia and that CLA was observed to be incorporated into muscle, liver and brain. Lower growth and higher liver lipid contents were observed in the CDHA-supplemented dietary fish group.