Abstract
This study aimed to examine the effects of dietary tuna hydrolysate supplementation on feed intake, growth, feed utilization and health status of Asian sea bass. Experimental diets included a high fish meal-based diet (HFM diet) containing 45% of fish meal, a low fish meal-based diet (LFM diet) in which 55% of fish meal protein was replaced with soybean meal and the LFM diet coated with 2.5% tuna hydrolysate (LFM + TH diet). Fish were fed diets for 8 weeks. Growth rate, feed intake, feed efficiency, protein efficiency ratio, nitrogen retention, intraperitoneal fat and serum albumin of fish-fed LFM + TH diet were significantly higher than those of fish-fed LFM diet (p < 0.05). No significant differences in carcass chemical compositions, serum cholesterol, triglyceride, aspartate aminotransferase, lysozyme activity, superoxide dismutase and trypsin and lipase activities were found in hepatopancreas and anterior intestine among the dietary treatments. Fish-fed LFM + TH diet displayed a longer length of distal intestine villi than those of fish-fed LFM + TH diet. No histopathological changes in the liver were observed in this study. The results suggest that dietary supplementation of 2.5% tuna hydrolysate is sufficient to enhance the diet palatability, which can increase the replacement levels of fish meal protein with soybean meal up to 55% in a low fish meal soybean meal-based diet without negative impacts on feed intake and growth performance of juvenile Asian sea bass.