Effect of Dietary n-6 and n-3 Fatty Acids on Growth, Fatty Acid Composition and Histological Changes of White Fish Coregonus lavaretus maraena

Abstract

A feeding experiment was conducted to characterize essential fatty acid deficiency and to determine the effect of dietary n-6 and n-3 fatty acids on growth and histological changes of white fish Coregonus lavaretus maraena. Growth, feed efficiency together with survival rate were lowest in fish fed a diet containing 5% 18: In-9 as a sole lipid source. On the otherhand, all parameters were effectively improved by supplementation with n-3 fatty acids, and were highest in fish receiving the diet containing n-3 highly unsaturated fatty acids (HUFA) greater than 0.5%. However, 18: 2n-6 was found to be ineffective for enhancing growth. Addition of 18: 2n-6 to 18: 3n-3 did not further improve growth and feed efficiency. The fish fed the 18: 1 n-9 diet showed swollen pale livers with abnormalities in histological analysis. This abnormal histological condition was improved by supplementation of 0.5% n-3 HUFA. The ratio of 20: 3n-9 to 22: 6n-3 in the fatty acid composition of polar lipid fractions from the livers, one of the EFA indices for freshwater fish, was highest in the EFA-deficient group and lowest in the fish receiving 1% n-3 HUFA in diet. These results indicate that n-3 fatty acids are essential for white fish. © 1989, The Japanese Society of Fisheries Science. All rights reserved.