Growth, fat metabolism and hepatic health in largemouth bass fed varying fat-level diets

This 60-day experiment investigated the influences of growth, fat metabolism and hepatic health of largemouth bass (Micropterus salmoides) fed varying fat diets. 225 fish (34 ± 0.04 g) were divided into three groups and fed diets with fat levels of 10 % (Low-fat diet, LFD), 14 % (Medium-fat diet, MFD) and 18 % (High-fat diet, HFD), respectively. The results revealed that fish fed HFD exhibited significantly better protein efficiency ratio (PER) and lower feed conversion ratio (FCR) than LFD group (P0.05). Dietary fat levels significantly decreased hepatosomatic index (HSI) of fish (P0.05). The contents of fat and ash in whole-body, and hepatic fat contents were increased with dietary fat levels (P0.05). Serum biochemical indexes and serum alanine aminotransferase (ALT) activity, liver glutathione peroxidase (GSH-Px) and catalase (CAT) activities were increased significantly with rising dietary fat levels (P0.05). The expression of srebp-1 and acc in liver were down-regulated, but atgl, aco and bax were up-regulated with rising dietary fat contents (P0.05). The histology of liver indicated the size and quantity of fat droplets increased with increment of dietary fat intake. Conclusion: the dietary fat levels of 14 %-18 % could be conducive to better growth of largemouth bass in this study.