Characterisation of Digestive Enzymes and In Vitro Screening of Feed Ingredients for the ew Hybrid Grouper, Epinephelus coioides (Hamilton 1822) × Epinephelus lanceolatus (Bloch 1790)

The new hybrid grouper [Epinephelus coioides (Hamilton 1822) × Epinephelus lanceolatus (Bloch 1790)] has been recently hybridised by fertilising the egg of orange-spotted grouper with sperm of giant grouper. Information on nutritional requirements for this hybrid is still limited. Characterisation of the main digestive enzymes (including pepsin, trypsin, chymotrypsin and amylase) as well as in vitro screening of feed ingredients suitable for the hybrid were therefore investigated in this study. The body weight of the hybrid was positively correlated with gastrointestinal weight (r = 0.8952, P 0.001, n = 30). The characteristic observation suggested that optimal conditions for studying digestive enzyme activities in hybrid grouper were: pH 1 and 4 at 40 ˚C for pepsin, pH 10 at 40 ˚C for trypsin, pH 10 at 35 to 45 ˚C for chymotrypsin and pH 8 at 50 ˚C for amylase. In vitro screening of 16 feed ingredients using digestive enzymes extracted from the intestine indicated that wheat gluten, soybean meal, squid liver meal and fish meal were good sources of protein while appropriate carbohydrate sources were broken rice, rice bran, wheat bran, wheat flour and corn meal. These findings can be used for understanding the nutritional requirement via the enzymatic analysis, whereas in vitro digestibility could provide information on the appropriate feed ingredients that can be used for the hybrid feed formulation.