Apparent digestibility coefficients of selected feed ingredients for Asian seabass, Lates calcarifer reared in recirculatory aquaculture system

Digestible nutrient-based feed formulations have become more prevalent in aquaculture, especially in intensive recirculatory aquaculture systems (RAS). In order to maximize growth performance and feed efficiency in Asian seabass (Lates calcarifer) raised in RAS while minimizing waste output, it is imperative to assess the apparent digestibility of nutrients from different feed ingredients used in the feed formulations. Accordingly, an eight-week study was conducted to analyse the apparent digestibility coefficients of nutrients in selected protein sources for Asian seabass, Lates calcarifer, reared in RAS. The reference diet consisted of commercial seabass feed with 47% crude protein. The test diets were formulated based on a 70:30 ratio approach for ingredient digestibility evaluation using fishmeal (FM), squid meal (SQM), soybean meal (SBM), corn gluten meal (CGM), wheat flour (WF), and broken rice (BR). The reference and test diets were finely ground for homogeneity, mixed with 0.5% commercial binder for stability, digestibility indicator (0.5% chromic oxide), and 2 mm pellets were produced. Growth of fish fed different diets was significantly affected owing to large variations in the inclusion levels of each ingredient. ADC of protein, lipid and energy varied from 81 to 93%, 62.8 to 90.1% and 81 to 90.3% respectively. FM and SQM exhibited significantly higher nutrient digestibility values, as fish are carnivorous. The higher nutrient digestibility of major plant-based protein ingredients suggests a higher quality of source materials. Overall, the present study provides information on the bioavailability of nutrients in animal and plant feedstuffs for Asian seabass reared in RAS.