Effect of eicosapentaenoic acid and docosahexaenoic acid in pollock liver oil on growth and fatty acid composition of rainbow trout.

Abstract

A feeding experiment was conducted to compare the effects of eicosapentaenoic acid (20:5ω3) and docosahexaenoic acid (22:6ω3) with that of linolenic acid (18:3ω3) on growth and fatty acid composition of rainbow trout. The growth rate was much reduced in fish kept on a diet containing 0.5% 18:3ω3. the replacement of 0.5%18:3ω3 with either 0.5%20:5ω3 or 0.5%22:6ω3 markedly increased the growth rate. This result indicates that 20:5ω3 has the same growth enhancing effect as 22:6ω3 and that not only 22:6ω3 but also 20:5ω3 has an EFA efficiency higher than 18:3ω3. The best weight gain was obtained in fish on a diet containing 0.25%of each of 20:5ω3 and 22:6ω3 respectively, indicating an additive effect between 20:5ω3 and 22:6ω3 on the growth of rainbow trout. The ratio of 20:3ω9 to 22:6ω3 in livers, an FEA index of rainbow trout, appeared as a low value, 0.4-0.5, in the fish fed diets containing either 20:5ω3 or 22:6ω3. This indicates a nearly normal FEA status, whereas the ratio of the fish receiving 0.5% 18:3ω3 was 0.8, which indicates an insufficient EFA status. Thus it has been demonstrated that both 20:5ω3 and 22:6ω3 have a biological efficiency or an EFA efficiency higher than of 18:3ω33 and that the growth enhancing effect of Pollock liver oil is due to an additive effect between 20:5ω3 and 22:6ω3 in its fatty acid fraction.