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Effects of dietary α-linolenic acid/linoleic acid ratio on growth performance, tissue fatty acid profile, serum metabolites and Δ6 fad and elovl5 gene expression in silver barb (Puntius gonionotus).

BACKGROUND
Silver barb (Puntius gonionotus) is a promising medium-sized carp for freshwater aquaculture in Asia. This study's aim was to investigate the ideal dietary α-linolenic acid (ALA): linoleic acid (LA) ratio for maximizing long chain polyunsaturated fatty acids (LC-PUFA) synthesis and their deposition in the muscle of silver barb, at par that of fish oil based control diet.


RESULT
Fish (11.07 ± 0.12 g of initial body weight) were fed for 60 days with five experimental iso-proteinous, iso-lipidic and iso-caloric diets, supplemented with linseed oil and peanut oil at varying levels to get ALA/LA ratios of 0.35, 0.51, 0.91, 2.04, 2.66 and a control diet prepared by supplementing fish oil. Dietary ALA/LA ratio did not influence the growth performance of fish. With increased dietary ALA/LA ratios LA content decreased and ALA content increased in muscle and liver of silver barb. The n-3 LC-PUFA level in muscle and liver were not influenced on feeding different ratios of ALA/LA, whereas n-6 LC-PUFA was decreased in the muscle and increased in the liver with increased dietary level of ALA/LA ratios. Increasing dietary ALA/LA ratio increased Δ6fad and elovl5mRNA expression in the liver, muscle, brain and intestinal tissues of silver barbs.


CONCLUSION
Silver barb possess the ability to elongate and desaturate ALA and LA to their end products EPA and DHA. The highest level expression of Δ6 fad and elovl5 mRNA at the dietary ALA/LA ratios of 2.66 suggests greater affinity of these enzyme towards ALA than LA in silver barb. This article is protected by copyright. All rights reserved.