Effect of Microencapsulated Fermented Catfish Waste Extract on Apparent Metabolizable Energy, Nutrient Digestibility,...

Microencapsulated fermented catfish waste extract (MFCWE) is a promising, circular-economy feed additive that may help replace antibiotic growth promoters while valorizing catfish-processing byproducts through fermentation and microencapsulation. This study evaluated graded dietary inclusion levels of MFCWE (0.5%-2.0%) on energy utilization, nutrient digestibility, digestive enzyme activity, and selected intestinal microbes in broilers. A completely randomized design was used with six treatments: basal diet (T-), basal diet + zinc bacitracin (100 ppm; T+), and basal diet supplemented with 0.5%, 1.0%, 1.5%, or 2.0% MFCWE (T0.5-T2). At day 35, birds were subjected to a metabolizable energy trial and sampling for digestibility, enzyme activity, and microbial counts. MFCWE affected AME (p = 0.003), AMEn (p = 0.007), and nitrogen retention (p < 0.001), with the highest AME/AMEn values observed at 1.5%-2.0% inclusion and the highest nitrogen retention at 1.5%. Dry matter and organic matter digestibility were highest at 1.5% MFCWE, representing increases of 8.6% and 7.6%, respectively, relative to T- (both p < 0.001), and were comparable to T+. Amylase activity increased with MFCWE (p = 0.005), while Staphylococcus aureus counts were reduced by 16.6% at 1.5% inclusion relative to T- (p = 0.003); total aerobic bacteria and Escherichia coli were not affected (p > 0.05). Overall, 1.5% MFCWE provided the most consistent improvements across endpoints, supporting its potential as a functional, microencapsulated feed additive and a value-added route for catfish-processing waste utilization.