Improvement in lipid metabolism and stress tolerance of juvenile giant grouper,Epinephelus lanceolatus (Bloch), fed supplemental choline

Six fish meal basal diets supplied with 0 (control), 0.25, 0.5, 1, 2.5 and 5 g kg^?1 of choline chloride, resulting in choline levels of 2.57, 2.67, 2.94, 3.84, 4.99 and 7.71 g kg^?1, respectively, were fed to giant grouper, Epinephelus lanceolatus, for 56 and 30 days to evaluate the growth and lipid metabolism, and stress tolerance respectively. In the first trial, fish fed different levels of choline‐containing diets for 56 days had no significant difference in weight gain, survival and feeding efficiency. Fish fed increased levels of dietary choline, however, tended to have decreases in the hepatic somatic index; lipids, triglycerides, and cholesterol in liver; and triglycerides and cholesterol in serum. A decrease of lipid content in dorsal muscle was recorded in fish fed the diets containing choline >2.94 g kg^?1. Additionally, dietary choline improved the reactions of fish to ammonia stress, including survival and behavioural responses, in fish fed diets containing choline levels >2.94 g kg^?1. These findings indicate that choline plays important roles in lipid metabolism and stress tolerance in giant grouper.