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).
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