Effect of triacylglycerols in formulated diets on growth and fatty acid composition in tissue of green abalone (Haliotis fulgens)

Abstract

Isocalotic formulated diets containing four different sources of triacylglycerols (olive, corn, linseed and cod liver oils) at three levels (1.5%, 3.0% and 5.0%, total added dietary lipid = 5.0%) and a crude protein content of 37.5% to 39.9% were fed to juvenile green abalone (Haliotis fulgens). Growth and fatty acid composition of the muscle tissue were compared to that of abalone fed a reference diet that contained no added lipids (0.25% total lipids). After 75 days of culture in a flow-through system, no significant differences in growth were found among abalone fed the different oil types. Responses to different dietary levels of lipid were significantly different but not to sources of oils. Maximum growth was achieved at a 1.5% inclusion of oil sources. It appears that abalone have a great capacity to synthesize lipid from carbohydrate sources. Results also suggest that abalone are capable of desaturation and elongation of 18 C polyunsaturated fatty acids (PUFAs) of the n - 3 and n - 6 family to 20:5n - 3 and 20:4n - 6. Synthesis of 22:6n - 3 from 20:5n - 3 is not reflected in the results. The lack of a growth response to the different levels of highly unsaturated fatty acids (HUFA) provided by the different oils included in the experimental diets may be due to an insufficient duration of the experiment to achieve an essential fatty acid deficiency. The relationship between fatty acid profiles of tissue and the diets fed to the abalone suggests that metabolic activity of the gut microflora is not a source of essential fatty acids. (C) 2003 Elsevier Science B.V. All rights reserved.