Soybean meal fermented with Lactobacillus acidophilus or a microorganism blend enhances intestinal condition without affecting growth performance of South American catfish ( Rhamdia quelen ) juveniles

This study evaluated the effects of soybean meal processed via solid-state fermentation with Lactobacillus acidophilus (FSML) or a microbial blend (FSMB) on growth performance, feed utilization, and intestinal condition of South American catfish (Rhamdia quelen) juveniles over 56 days. The completely randomized design comprised five dietary treatments (four replicates): a control diet (0%) and four diets replacing fishmeal with 7% or 14% of FSML or FSMB. Fermentation improved nutritional quality by increasing soluble peptides, promoting bacterial proliferation, and reducing pH. Dietary inclusion up to 14% did not affect growth performance compared to the control (p>.05). Furthermore, fermented soybean meal enhanced intestinal goblet cell density (p<.05), while 7% FSML increased amylase activity (p=.002). Thus, fermented soybean meal safely replaces up to 14% fishmeal as a functional protein source, improving mucosal condition without compromising performance.