The use of agro-industrial by-products as functional feed additives represents a promising strategy to enhance sustainability and digestive efficiency in aquaculture. This study investigated the dose-dependent effects of bromelain derived from pineapple processing waste on digestive physiology, nutrient utilization, and economic performance in snakeskin gourami, Trichopodus pectoralis Regan, 1910. Fish (95-98 g) were fed diets supplemented with 0, 4, 8, or 12% bromelain for 90 days in a completely randomized design. Growth performance, survival, and feed utilization were not significantly affected by dietary treatments (p > 0.05), suggesting that exogenous protease supplementation did not enhance growth under nutritionally adequate conditions. However, bromelain inclusion elicited a pronounced, dose-dependent modulation of digestive enzyme activity. The 8% supplementation significantly enhanced pancreatic protease and amylase activities. This indicates improved digestive capacity and better nutrient assimilation. In contrast, the 12% inclusion level was associated with reduced activity of specific enzymes, suggesting feedback inhibition or enzymatic imbalance at excessive doses. Despite the absence of significant growth responses, a progressive increase in benefit-cost ratio was observed with increasing bromelain inclusion, reflecting improved production efficiency. Variations in muscle composition were primarily attributed to moisture-associated dilution effects rather than reduced protein deposition. Collectively, these findings demonstrate that bromelain derived from pineapple waste functions as a physiologically active feed additive that modulates digestive processes in a dose-dependent manner, with 8% identified as the optimal inclusion level. This study provides mechanistic evidence supporting the valorization of agro-industrial waste as a functional input in sustainable aquaculture systems.
