Effects of dietary lipid levels on growth, lipid deposition, oxidative stress and hepatic morphological changes in giant grouper, Epinephelus lanceolatus

The present study examined the effects of dietary lipid levels on growth performance, lipid deposition, oxidative stress and liver morphological changes in giant grouper, Epinephelus lanceolatus. Five isonitrogenous diets containing graded lipid levels (100, 125, 150, 175 and 200 g/kg diet) were applied to triplicate groups of grouper (mean weight: 17.59 ± 0.14 g) in a seawater recirculation system for 56 days. Dietary lipid levels from 100 to 200 g/kg exhibited no influence on weight gain, specific growth rate, protein efficiency ratio and feed efficiency of the fish. Grouper whole-body and hepatic total lipid content, intraperitoneal fat ratio and oxidative stress (malondialdehyde content) increased linearly (p < 0.05) with escalating dietary lipid levels, reaching the highest values for a fish fed diet with 200 g/kg lipid content. In comparison with the observations in the liver of 100–125 g/kg lipid groups, the liver sections from the 175–200 g/kg lipid groups showed more numerous and larger vacuoles and the presence of round or elliptical hepatocytes. The results indicated that giant grouper could tolerate dietary lipid levels of up to 200 g/kg without exhibiting any negative impacts on growth performance in the 56-day feeding trial. According to the results of intraperitoneal fat, hepatic lipid content, oxidative stress and liver morphology, a dietary lipid level no higher than 150 g/kg is recommended for this species.