Dietary corn silk enhances growth, immunity, and gene expression in Nile tilapia (Oreochromis niloticus) cultured in a biofloc system.

Abstract

This study evaluates the effects of dietary corn silk (Zea mays L.) supplementation on the growth performance, digestive enzyme activity, immune response, and gene expression of Nile tilapia (Oreochromis niloticus) reared in a biofloc system. Three hundred juvenile Nile tilapia were fed diets supplemented with corn silk (CS) at different inclusion levels (0, 5, 10, 20, and 40 g kg^-1) for eight weeks. The results showed that fish fed 10 g kg^-1 corn silk exhibited the highest final weight, weight gain, and specific growth rate, while feed conversion ratio was significantly improved compared to the control group (P < 0.05). Digestive enzyme activity, including amylase, lipase, protease, and trypsin, was significantly elevated in fish receiving 10 g kg^-1 corn silk, suggesting enhanced nutrient digestion and absorption. Serum and skin mucus immune parameters, such as lysozyme and peroxidase activity, were markedly higher in supplemented groups, particularly at 10 and 20 g kg^-1 inclusion levels. Additionally, alternative complement hemolytic activity (ACH50) was significantly upregulated in fish fed 20 g kg^-1 corn silk. Gene expression analysis revealed that growth-related (ghrelin, galanin, npya, and ef-α), immune-related (il1β, tnfα, nfκb, and mhciiα), and antioxidant-related (hsp70, gpx, and nrf2) genes were significantly upregulated in fish fed 10 g kg^-1 corn silk. These findings highlight the potential of corn silk as a functional feed additive to enhance growth, digestion, and immune responses in Nile tilapia, contributing to sustainable aquaculture practices. Further research should explore optimal inclusion levels and the long-term effects of corn silk supplementation.