Effect of ethyl linoleate, ethyl linolenate and ethyl esters of highly unsaturated fatty acids on essential fatty acid deficiency in rainbow trout

The essential fatty acid requirement of milkfish (Chanos chanos Forsskal)

The essential fatty acid (EFA) requirement of milkfish was examined by a 12-week feeding trial using defined, purified diets at water temperature of 28-29°C and salinity of 32‰. The test diets contained varying levels of 18:0 (triglyceride form, TG), 18:3(n-3), 18:2(n-6) and (n-3) highly unsaturated fatty acids (n-3 HUFA). Milkfish juveniles were starved for 7 days and were than fed lipid-free diet for 30 days before the initiation of feeding trials. Low growth and feed efficiency together with high mortalities were observed in fish fed the lipid-free diet as well as in the EFA-deficient diet. Supplementation of 2% 18:2(n-6) to the tristearin based diet did not improve growth rate of milkfish as effectively as feeding with (n-3) fatty acids. The highest weight gain was obtained in milkfish fed a combination of 5% 18:0 + 1.0% 18:3(n-3) + 0.5% 20:5(n-3) + 0.5% 22:6(n-3) although the supplementation of 2% 18:3(n-3) alone or combination of 0.5% 20:5(n-3) + 0.5% 22:6(n-3) to the tristearin based diets were also effective for improvement of growth. Thus, (n-3) fatty acids, such as 18:3(n-3) and (n-3)HUFA were nutritionally more important than 18:2(n-6) for milkfish. The fatty acid composition of the polar lipids from whole body of milkfish juveniles fed the various test diets were influenced by the composition of the dietary fatty acids.

[Use of solid fat in dry mixed feed for rainbow trout (Salmo gairdneri). 2. Fatty acid composition of feed and tissue lipids]

The effect of supplemental dietary fat on the fatty acid composition of some tissue lipids of rainbow trout fingerlings was studied. Data showed that dietary fatty acids were deposited nearly unchanged in the adipose tissue. The level of eicosapentaenoic acid, however, dropped significantly. Muscle showed remarkable capacity for deposition of dietary fat, while only minor changes were observed in the fatty acid composition of liver lipids. Levels of some polyenoic acid (e.g. 18: 2 omega 6, 20:4 omega 6, 20:5 omega 3, 22:6 omega 3) showed, that the fish converted lower unsaturated fatty acids to highly unsaturated fatty acids. It was observed that dietary acids had little effect on the fatty acid composition of tissue phospholipids. This result shows, that 17% fat in the diet are tolerated by trout, without alterations in the fat composition of the liver tissue. Probably the low rearing temperature (11 degrees C) had a more pronounced effect on the fatty acid composition of phospholipids than the diet.