Effects of dietary LNA/LA ratio on growth, hepatic fatty acid profiles and △6fad, elovl5 mRNA expression in common carp (Cyprinus carpio)

To evaluate the effects of dietary α-linolenic acid (LNA, 18:3n-3)/ linoleic acid (LA, 18:2n-6) ratios on growth performance and LC-PUFA biosynthesis in common carp, we designed five iso-nitrogenous and iso-energetic diets for eight weeks of feeding trial. The control diet (D1) was only supplemented with fish oil as lipid source, while the mix of peanut oil and perilla oil with varying LNA/LA ratios of 0.02, 0.46, 1.09 and 1.53 was used as lipid source for the experimental groups D2, D3, D4 and D5, VO (vegetable oil) diets, respectively. The results showed that, there were no differences among control group and VO groups in WGR, SGR and FCR. Compared with the control group, the hepatic LC-PUFA levels were significantly low in VO groups, whereas, the hepatic Δ6 fad-a and elovl5-a mRNA expression levels were significantly improved by VO diets. Among the four VO groups, the WGR and SGR were significantly affected by dietary LNA/LA ratios, with higher growth in D4 and D2 groups. Additionally, the hepatic LC-PUFA levels, Δ6 fad-a and elovl5-a mRNA expression levels were higher in the fish fed higher ALA/LA ratios diets. In particular, the highest hepatic LC-PUFA levels were observed in D4 groups, and consistent with this, hepatic Δ6 fad-a and elovl5-a mRNA with the highest level were also showed in D4 groups. The results indicate that VO diets have a negative effect on the hepatic LC-PUFA levels in common carp. However, the optimal balance LNA/LA supplement (1.09∶1) have been successful in raising the efficiency of LC-PUFA production by improving the hepatic Δ6 fad-a and elovl5-a mRNA expression, and decreasing the negative impact of VO diets on tissue LC-PUFA concentration in this fish species.