New approach to the development of tailor-made feed for fish larvae using Zebrafish Danio rerio as a model

Protein hydrolysates have been used extensively as dietary protein for larval fish. Typically, they are expensive, difficult to produce, and show varying results when utilized for different species. This study proposed a practical hydrolysis method that utilizes endogenous enzymes within the body to "auto-hydrolyze", or digest its tissue proteins with its own endogenous enzymes, and produce a fishmeal tailored to nutritional requirements and absorptive capacity of larval fish. The objectives for this experiment were to determine the: 1) effect of the proposed hydrolysis method on tissue protein breakdown level; and 2) effect of dietary inclusion of obtained hydrolysates on larval growth performance, using Zebrafish (Danio rerio). Whole-body adult Zebrafish were utilized to produce an unhydrolyzed fishmeal, and three fishmeals hydrolyzed for 1, 2, and 3 h, respectively. Three diets were formulated, defined by their dietary protein supply. The Unhydro diet contained unhydrolyzed Zebrafish meal. The 50% Hydro diet contained 50% Zebrafish meal hydrolysates and 50% unhydrolyzed Zebrafish meal. The 100% Hydro diet contained 100% Zebrafish meal hydrolysates. Five groups were utilized in this study, with three groups receiving one of the produced Zebrafish meal-based diets. Larvae fed a commercial starter diet and Artemia, respectively, were included as reference groups. Larval fish were randomly stocked into tanks (100 fish per tank) at 3 days-post-hatch (dph), and the trial was carried out until 18 dph. Electrophoretic analysis showed that the proposed hydrolysis method was able to efficiently hydrolyze the protein within Zebrafish body. The feeding trial results found no significant differences in weight, total length, or survival between the Unhydro, 50% Hydro, and 100% Hydro groups. The proposed hydrolysis method provides a practical and potentially cost-effective approach to producing species-specific fishmeal hydrolysates. Further research is necessary to determine whether the produced hydrolysates can improve the growth of larval fish in other species.