Effect of flaxseed oil in diet on fatty acid composition in the liver of Nile Tilapia (Oreochromis niloticus)

SUMMARY. This study analyzed the effects of different concentra-tions of flaxseed oil (FO) on the proximate composition and the con-tents of alpha-linolenic acid (LNA, 18:3n-3), eicosapentaenoic (EPA, 20:5n-3), and docosahexaenoic (DHA, 22:6n-3) fatty acids in the liver of cultured Nile tilapia (Oreochromis niloticus). During the five-month culture period, tilapias were given diets with incremental con-centrations of FO (0.00%; 1.25%; 2.50%; 3.75%, and 5.00%) as a replacement of sunflower oil (control). There was no significant difference in moisture and ash content in the liver between treat-ments. Protein values ranged from 12.1 % (treatment II) to 13.9% (treatment V) and total lipids ranged from 5.6 % (treatment V) to 7.2 % (treatment II). There was no significant difference between most treatments. Fatty acid methyl esters (FAMEs) were quantita-tively analyzed by capillary gas chromatography against a C23:0 in-ternal standard. Variations in concentrations (in mg g-1 of total lip-ids) of fatty acids between treatment I and treatment V ranged from 4.2 to 51.2 (LNA), from 0.2 to 2.3 (EPA), and from 10.6 to 56.2 (DHA), respectively. This experiment demonstrated that increasing amounts of LNA in feed may markedly increase the amounts of LNA, EPA, and DHA in the liver of Nile tilapia