Partial replacement of soybean meal with fermented corn husk enhances growth, digestive enzymes, immune response, and growth-, immune-, and antioxidant-related gene expression in Nile tilapia (Oreochromis niloticus) reared in biofloc system

Abstract

This study investigated the effects of dietary fermented corn husk (FCH) on growth performance, digestive enzyme activities, immune responses, and gene expression in Nile tilapia (Oreochromis niloticus). A total of 300 fingerlings (40.18 ± 0.18 g) were randomly distributed into 15 tanks (three replicates per treatment, 20 fish per tank) and fed diets containing 0 (control), 2.5, 5, 10, or 20 g kg−1 FCH for eight weeks under biofloc conditions. Results showed that fish fed 10 and 20 g kg−1 FCH had significantly greater final weight, weight gain, specific growth rate, and lower feed conversion ratio compared to the control. Activities of digestive enzymes including amylase, lipase, protease, and trypsin were significantly elevated, especially in the FCH10 and FCH20 groups. Mucosal and serum immune responses, such as skin mucus and serum lysozyme, peroxidase, and ACH50 activities were markedly improved in FCH-fed fish, with optimal responses observed at 10 g kg−1. Expression of immune-related (il-1β, tnf-α, mhcii-α, nfkb), antioxidant-related (hsp70, gpx, nrf2), and appetite-regulating genes (ghrelin, npy-α, and galanin) was significantly upregulated in the FCH5 and FCH10 groups. Additionally, ef1-α, a marker for protein synthesis, was significantly enhanced in the FCH5 and FCH10 groups, indicating improved anabolic activity, but declined at 20 g kg−1. These findings highlight FCH, particularly at 10 g kg−1, as a sustainable feed additive that improves growth, digestive efficiency, immunity, and molecular health in Nile tilapia.