Abstract
One of the most consumed freshwater fish in South America is Nile tilapia. The present study examined the effects of flaxseed oil (FO), source of alfa-linolenic acid (LNA), on the total lipid composition and polyunsaturated fatty acid, n-6 and n-3 PUFA, contents on Nile tilapia (Oreochromis niloticus) liver. Tilapias were given diets with increasing levels 0.00, 1.2, 2.50, 3.75 and 5.00% (w w-1) of FO as a replacement of sunflower oil for five months. Fatty acids analysis of methyl esters revealed 45 fatty acids common to all treatments. The increase of flaxseed oil resulted in a decrease in total n-6 PUFA (35.1 to 21.1%) and an increase in n-3 PUFA (3.3 to 18.5%). The diet with LNA underwent sequential desaturation and elongation in liver, leading to an increase in all n-3 PUFA and a decrease in n-6/n-3 ratios (10.7 to 1.1). The manipulation of fatty acids with FO may be used to increase n-3 PUFA and to help balance n-6/n-3 PUFA in dietary supplements, thus, the liver tilapia becomes one product with major nutritional value.
Highlights
Tilapia is one of the most cultured freshwater fish worldwide (YASMIN et al, 2004)
Five treatments in five duplications were used with 125 Nile tilapias (Oreochromis niloticus) with initial mean individual weight of 88 ± 6 g distributed in 25 ponds (1000 L each)
FAME was separated by gas chromatography using a Varian 3300 (USA) gas chromatographer fitted with a flame ionization detector and a fused-silica DB-WAX capillary column (30 m x 0.25 mm i.d.) (J and W Scientific, Folsom, CA)
Summary
Tilapia is one of the most cultured freshwater fish worldwide (YASMIN et al, 2004). Recent studies indicate that some fish parts not used as food are appropriate for human nutrition (ARRUDA, 2004) and may be used in fish oil extraction. The importance of fish as a source of polyunsaturated fatty acids (PUFA), n-3 fatty acids in human nutrition is widely recognized (SIMOPOULOS, 2004). These fatty acids (n-3 PUFA) have been associated to numberless benefits. Linoleic acid (LA, 18:2n-6) and alpha-linolenic acid (ALA, 18:3n-3) are metabolized by the same sequential desaturation and elongation enzyme systems, which results in the production of long-chain PUFA n-3 and n-6 series (HENDERSON; TOCHER, 1996; STUBHAUG et al, 2005). Flaxseed oil is one of the world’s most important vegetable sources of ALA (WANASUNDARA; SHAHIDI, 1994), a precursor of the long chain n-3 PUFA series, in freshwater fish (HENDERSON; TOCHER, 1996). This work investigated the influence of the incremental addition of flaxseed oil as a substitute of sunflower oil in feed on the concentrations of fatty acids, n-3 and n-6 in the liver of Nile tilapias (Oreochromis niloticus) maintained in captivity for five months
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