Abstract

Omolo Kevin Mbogo, Onyango Arnold, Magoma Gabriel, Munguti Jonathan, Masinde WP and Ogila Kenneth

This study evaluated the effect of varying proportions of linseed and olive oils in fish diets on the fatty acid composition of tilapia and catfish liver and muscles under aquaponics culturing system after 150 days of feeding period. Experimental diets contained linseed, sunflower and olive oils at a varying composition of between 0 to 100% and commercial diet as a control feed. Gas chromatography was used to analyze fish tissue fatty acid profiles. Significantly high composition of n-3 fatty acids were observed in tilapia fed diet 1 (p<0.05) with DHA (C22:6) being the dominant n-3 fatty acids at 12.2% and 10.8% in tilapia muscles and liver respectively. In catfish, muscle and liver had 10.4% and 9.7% DHA content respectively. The muscle accumulation of n-3 fatty acid was significantly higher than liver in both fish species and efficiency in their retention and relative resistance of DHA to β-oxidation in the fish muscles. In both tilapia and catfish, the tissue n-3 fatty acids decreased with the reduction in linseed oil proportion in the diet feed suggesting direct influence of dietary oil composition on tissue fatty acid composition.