Alterations in feeding preference and gastric emptying of giant freshwater prawn (Macrobrachium rosenbergii) following administration of varying quantities of fermented soybean meal

Abstract

Abstract This study aimed to investigate the impact of partially substituting fish meal (FM) and soybean meal (SBM) in the diet with fermented soybean meal (FSBM) on growth, feeding preference, protease activity, and their correlation with gastric evacuation in giant freshwater prawn, Macrobrachium rosenbergii. A 55-day feeding trial was conducted with eight isonitrogenous and isoenergetic diets, followed by a gastric emptying experiment. The results showed that the control group (containing 30% FM and 18% SBM) exhibited the highest feeding preference index, while the preference index of all diets demonstrated an initial decrease followed by an increase and subsequently a decline with increasing levels of supplemental fermented soybean meal. The SBM free group (almost devoid of soybean antigen proteins) showed the lowest preference index. Notably, there was no significant difference in feeding preference before and after domestication of the feed, and it was consistent with the trend of feeding rate. All the presented findings indicated that the inclusion of fish meal is a crucial factor influencing the feeding preference of M. rosenbergii. The excessive incorporation of fermented soybean meal in the diet led to an aversion towards feeding, which significantly contributes to the decline in growth rate.Short-term domestication (55 days) did not significantly alter the feeding preference of M. rosenbergii towards fermented soybean meal. However, when fermented soybean meal replaced fish meal and soybean meal, the individual action or interaction between antigenic proteins and other anti-nutritional factors resulted in varying changes in digestive enzyme activity and gastric evacuation dynamics.