Testing Protein Digestibility in Red Grouper Epinephelus Morio using In Vitro and In Vivo Methods

Abstract

The digestibility of pre-selected ingredients was evaluated for Epinephelus morio using pH-stat and multi-enzyme extract (stomach, intestine, and ceca). The degree of hydrolysis (DH) was tested with acid and alkaline proteases using crustacean meals, squid meal, fish protein concentrate (FPC), fish meal, dried whey, as well as canola paste (w/ or w/o phytase), soybean meal (w/ or w/o phytase), soyprotein concentrate (SPC), and wheat gluten. SPC produced DH values between 3.6-4.1%, obtained from the three different parts of the digestive tract. Canola paste produced high DH in the stomach by adding phytase to 0.8 and 2% feed. This process was repeated under alkaline conditions for DH, with 0.6-2.6% in the pyloric ceca, and 1-2.2% in the intestine. The DH from stomach with crustacean meals (shrimp meal and crab meal) ranged from 32-87%, while values for dried whey from the ceca and intestine ranged from 6-7.4%. It did not differ from crab meal with values of 4.5 and 8.7% from pyloric ceca and intestine respectively. Based on the above results, 4 diets were developed using shrimp meal, dried whey, soy protein concentrate, and canola+phytase. The DH, FAA (fish amino acid) and SDS-PAGE (analysis of protein gels) for each diet were analysed. After an in vivo test, results on juveniles fed whey protein diet (WPd) and CPd+ ranked high (95% and 92% respectively) compared with other treatments. pH-Stat provided consistent results regarding digestibility of selected protein sources. Therefore, dried whey, shrimp meal, and canola+phytase ranked first to be included in E.morio feed formulation with a pool of 55% of these components, complemented with a minimum of fish meal, FPC, grains and wheat gluten