Abstract
The present study evaluated the impact of varying dietary linseed oil composition on growth, survival and tissue polyunsaturated fatty acids (PUFA) profiles in Nile tilapia (Oreochromis niloticus). Five iso-nitrogenious diets with varying linseed and sunflower oil concentrations were formulated and fish fed twice daily to for 3 months. Commercial diet was used as a control in triplicate tanks set for each diet treatment. Growth parameters were measured from changes in body weight and length. A 75:25 ratio of sunflower oil to linseed oil gave a better survival and specific growth rate than 100% linseed oil or 100% sunflower oil. Tissue PUFA composition were determined using gas chromatography. High dietary linseed oil composition (100%) resulted into significantly high (P<0.05) total n3 fatty acids (9.9-25%) and DHA (1.8-7.9%) in muscles whereas liver n3 fatty acids and DHA composition ranged between 9.3-25.5 and 0.7-2.6%, respectively. Muscle and liver n3/n6 ratio ranged between 0.7-2.2 and 0.7-2.6 while tissue arachidonic acid (ARA 20.4 n6) content ranged between 2.6-3.5% in muscles and 3.4-4.5% in the liver. ARA 20.4 n6 values were low relative to the dietary precursor, linoleic acid, LA, 18.2 n6. Fatty acid deposition in the tissues increased with the feeding period with the third feeding month recording significantly higher DHA, total n3 and n3/n6 ratio. Based on the result, dietary linseed oil > 50% reduced growth and survival rate in tilapia, however, it increased tissue accumulation of essential fatty acids which also increased with the length of feeding period. Key words: Growth, Tilapia, n3 fatty acids, linseed oil, polyunsaturated fatty acids (PUFA).
Highlights
IntroductionWith the proven benefits of omega 3 highly unsaturated fatty acids (n3-highly polyunsaturated fatty acids (HUFA)) (Kris-Etherton et al, 2000; Gebauer et al, 2006; Kusunto et al, 2007), numerous governmental and non-governmental organizations across the world currently advise increased fish intake as a means of improving the health of their citizens (Munguti et al, 2014)
Proximate composition analysis of experimental diets and fatty acid composition of tilapia muscles and liver were done in Food Biochemistry laboratory, Food Science department-Jomo Kenyatta University of Agriculture and Technology (JKUAT)
Survival and specific growth rate significantly increased with reduction of dietary linseed oil
Summary
With the proven benefits of omega 3 highly unsaturated fatty acids (n3-HUFA) (Kris-Etherton et al, 2000; Gebauer et al, 2006; Kusunto et al, 2007), numerous governmental and non-governmental organizations across the world currently advise increased fish intake as a means of improving the health of their citizens (Munguti et al, 2014). Quality and affordable feeds are integral component of sustainable intensive and semiintensive aquaculture systems (Munguti et al, 2014). It is predicted that within a decade or so, fish oil production may not be sufficient to meet the demand of aquaculture (FAO, 2007). The introduction of alternative lipid sources is necessary to enable sustainable aquaculture development (Jordal et al, 2007; Bouraoui et al, 2011)
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