Trypsin encapsulated nanoparticle to improve growth performance in Labeo rohita (Hamilton) fingerling fed plant-based diets

Abstract Terrestrial plant-derived ingredients are increasingly used as alternative protein sources in aquaculture feeds. However, their nutrient availability is often limited due to poor digestibility, the presence of antinutritional factors, and imbalanced nutrient profiles, which can impair digestion, absorption, and growth. Supplementation with exogenous enzymes represents an effective method to improve the nutritional value of plant-based diets. A 60-day feeding experiment was undertaken to examine the dietary influence of nano-trypsin on the growth, digestive, and metabolic enzyme activities of Labeo rohita fingerlings (average weight 9.72 ± 0.18 g) fed a plant-based diet. Nano-trypsin was developed by encapsulating trypsin in chitosan nanoparticles using the ionic gelation method. Three dietary protein levels (20%, 25%, and 30%) were used to formulate six experimental diets, with or without nano-trypsin supplementation. The resulting nano-trypsin particles exhibited a size of 256.3 ± 3.21 nm, a zeta potential of 29 ± 0.0 mV, and a loading capacity of 83%. Fish fed nano-trypsin diets showed significantly improved %WG (54.85%–66.89%), SGR (0.73%–0.85% day⁻1), FCR (2.26–2.62), PER (1.48–1.91), and ANPU (26.05–39.54%) compared to bare trypsin and controls. Notably, fish receiving 20% and 25% dietary protein with nano-trypsin performed comparably to those fed 30% dietary protein without enzyme supplementation. Nano-trypsin supplementation significantly enhanced the intestinal protease, lipase, and ALP activities. The activities of metabolic enzymes such as LDH, AST, ALT, and MDH in liver and muscle tissues were considerably reduced in nano-trypsin-fed groups. These findings indicate that dietary nano-trypsin improves growth, digestive function, and metabolic efficiency when incorporated into the plant-based diet of L. rohita fingerlings.