Effects of dietary carbohydrate to lipid ratio on growth, feed utilization, body composition and digestive enzyme activities of golden pompano (Trachinotus ovatus)

An 8-week feeding trial was conducted to investigate the effects of dietary carbohydrate to lipid ratio (CHO: L) on growth, feed utilization, body composition and digestive enzyme activities of golden pompano, Trachinotus ovatus. Five iso-nitrogenous (450g/kg protein) and iso-energetic (19MJ/kg gross energy) diets with varying CHO: L ratios of 0.68, 1.02, 1.62, 2.61 and 4.35, respectively, were fed to triplicate groups of 30 fish (average 13.8 +/- 0.1g). Results showed that dietary CHO: L ratios did not show any significant influence on survival of golden pompano (p>.05) but significantly affected its growth performance and feed utilization (p<.05). Fish fed diets with CHO: L ratios at 1.62 and 2.61 exhibited the highest final body weight, weight gain ratio, specific growth rate, feed efficiency ratio and protein efficiency ratio. Fish body lipid and liver glycogen contents were also significantly influenced by CHO: L ratio (p<.05). Hepatic amylase activity increased firstly and then decreased as the dietary CHO: L ratio increased, while lipases activity decreased with increasing dietary CHO:L level. The regression model analysis showed that the most suitable dietary CHO: L ratio (protein 450g/kg) to reach the highest weight gain ratio is 2.38.