Effects of hydrolyzed hairtail protein partially replacing fish meal in diets on growth and protein turnover rate for hybrid grouper (Epinephelus fuscoguttatus♀×E. lanceolatus♂)

Abstract

The high protein content and digestibility of hydrolyzed hairtail protein (HHP) promise a superior protein source for aquatic animal diets. In this experiment, the feasibility of HHP as an alternative for fishmeal (FM) in diets of hybrid grouper (Epinephelus fuscoguttatus♀×E. lanceolatus♂) was evaluated by exploring its impact on growth and protein turnover rate. For this, three iso-nitrogenous and iso-energetic extruded diets were formulated: one with FM (33 %, HHP0); two with 10 % (HHP1) and 20 % (HHP2) FM protein replaced by HHP. After a 60-day feeding trial, an independent effect of dietary HHP levels on grouper growth performance, body composition, and nutrient retention efficiency was recorded. However, a second-order increase in the hepatosomatic index (HSI) and dry matter apparent digestibility coefficient (ADC) was plotted with increasing dietary HHP levels. Furthermore, results showed no adverse effect on protein turnover rate in muscle tissue at different dietary HHP levels, while the relative contribution ratio (RCR) from HHP on growth was lower than that from the equal amount of FM. Overall, our finding indicated that up to 20 % FM protein could be replaced by HHP without adverse effects on growth, body composition, nutrient retention efficiency, digestibility coefficient, and protein turnover rate.