Effects of dietary lipids on the fatty acid composition of triglycerides and phospholipids in tissues of white sturgeon

Abstract

Eight purified diets were fed to juvenile white sturgeon, Acipenser transmontanus Rick, for 9 weeks to investigate the effect of dietary lipids on the fatty acid composition of phospholipids and triglycerides from muscle, liver and brain. The diets contained 150 g kg-' of oils from canola, corn, cod liver, lard, linseed, soybean, safflower, or a control mixture (corn oillcod liver oilAard, 1 : I : 1, by wt). Dietary lipids significantly (P I 05) affected the composition of tissue triglycerides and phospholipids. Tissue triglyceride fatty acid composition ranged widely, in parallel with the dietary lipids, while phospholipids changes were more conservative. Brain phospholipid fatty acid composition was less responsive to diet compared with that in muscle and liver. Considerable amounts of n-6 and n-3 long chain polyunsaturated fatty acids (> ClO) were found in triglycerides and phospholipids with all diets, demonstrating that white sturgeon can desaturate and elongate linoleic acid (1 8:2n-6) and linolenic acid (18:3n-3). Further, the products of the A6 desaturase, i.e. 18:3 n-6 and 18:4n-3, were relatively abundant in triglyceride, suggesting that the A6 desaturase might not be a limiting step in the process in white sturgeon. Nevertheless, accumulation of both EPA and DHA was greater in the sturgeon fed fish oil than those fed linseed oil, indicating that muscle triglyceride EPA and DHA levels are best enhanced by diets rich in preformed EPA and DHA.