Requirements of Tilapia zillii for essential fatty acids

The requirements of essential fatty acids (EFA) for Tilapia zillii were examined by feeding diets with several types of lipids and with different levels of ω6 and ω3 fatty acids. The addition of 18:2ω6, 20:4ω6, 18:3ω3 and 20:5ω3 to the diet containing 12:0 as a basal lipid improved the weight gain of T. zillii. However, the growth-promoting effects of 18:2ω6 and 20:4ω6 were superior to those of 18:3ω3 and 20:5ω3. These data indicated that T. zillii requires ω6 fatty acids rather than ω3 fatty acids. The dietary requirement of T. zillii for 18:2ω6 or 20:4ω6 was found to be about 1.0% in the diet. In the groups of T. zillii fed with the EFA-deficient diets, the levels of 20:3ω9 and 18:1ω9 increased, but they were decreased by the supplementation of either 18:2ω6 or 20:1ω6. Also, the supplementation of 18:2ω6 to the diets increased the proportion of 20:4ω6 in polar lipids of Tilapia bodies, indicating that T. zillii probably converts 18:2ω6 to 20:4ω6.