Effect of Dietary Lipid on the Growth, Fatty Acid Composition and △5 Fads Expression of Abalone （Haliotis discus hannai Ino） Hepatopancreas

This study investigated the effect of dietary lipid on the growth, fatty acid composition and △5 fatty acyl desaturase genes （Fads） expression of juvenile abalone （Haliotis discus hannai Ino） hepatopancreas. Six purified diets were formulated to con- tain tripalmitin （TP）, olive oil （OO, 72.87% 18：1n-9）, grape seed oil （GO, 68.67% 18：2n-6）, linseed oil （LO, 70.48% 18：3n-3）, ARA oil （AO, 41.81% ARA） or EPA oil （EO, 44.09% EPA and 23.67% DAH）. No significant difference in survival rate was observed among abalone fed with different diets. Weight gain rate （WGR） and daily growth rate of shell length （DGRsL） were significantly increased in abalone fed with diets containing OO, AO and EO, but decreased in abalone fed with LO diet （P〈0.05） in comparison with those fed with TP. High level of dietary 18：2n-6 resulted in higher content of n-6 polyunsaturated fatty acids （PUFAs） in abalone fed with GO than those fed with TP, OO, LO and EO （P〈0.05）. n-3 PUFAs in abalone fed with LO was significantly higher than those in abalone fed with TP, OO, GO and AO （P〈0.05）. The highest contents of 20：1n-9 and 22：1n-9 were observed in abalone fed with OO. The expression of △5 Fads in hepatopancreas of abalone was enhanced by high concentration of 18：3n-3 and suppressed by dietary LC-PUFAs; however it was not affected by dietary high concentration of 18：1n-9 or 18：2n-6. These results provided valuable information for understanding the synthesis of LC-PUFAs and nutritional regulation of △5 Fads expression in abalone.