1996 年 62 巻 6 号 p. 945-949
Juvenile yellowtail Seriola quinqueradiata were fed five isonitrogenous and isoenergetic diets which contained increasing levels of carbohydrate (3-24%) and decreasing levels of lipid (16-8%) and a high protein control diet for 30 days. Growth, body composition, and hepatic enzyme activities were determined to clarify the metabolic response to dietary carbohydrate and lipid. Growth, feed conversion, and protein-sparing effect were lowest in fish fed the highest-carbohydrate lowest-lipid diet, and these parameters tended to increase with decreasing dietary carbohydrate to lipid ratios. In fish fed high lipid diets, the activities of hepatic glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, malic enzyme, glucose-6-phosphatase, and alanine aminotransferase together with glycogen content were markedly lower, while hepatic fat and plasma free fatty acid concentrationswere higher than in those fed the control diet. These findings suggest that dietary lipid depressed hepatic lipogenesis, gluconeogenesis, and amino acid degradation while it was effectively utilized asan energy source. These metabolic responses seem to explain the yellowtail's high capability to utilize dietary lipid and its high protein-sparing effect.
