Effects of Dietary Wedelia chinensis (Osbeck) Merr. Extract on Growth Performance, Feed Utilization, Antioxidant Status, and Innate Immunity in Nile Tilapia (Oreochromis niloticus)

Plant-derived additives are increasingly explored as functional aquafeed ingredients for supporting fish performance and physiological condition. This study evaluated the effects of dietary Wedelia chinensis extract (WCE) on growth performance, feed utilization, antioxidant status, innate immune-associated biomarkers, and immune- and antioxidant-related gene expression in Nile tilapia (Oreochromis niloticus). Juvenile fish with an initial body weight of 14.31 ± 0.03 g were fed diets supplemented with WCE at 0, 5, 10, 15, or 20 g kg−1 diet for eight weeks. Growth indices, somatic indices, serum and hepatic antioxidant biomarkers, mucosal and systemic innate immune-associated parameters, and liver and intestine gene expression were assessed. Dietary WCE improved final weight, weight gain rate, specific growth rate, and feed conversion ratio compared with the control, with WCE10 showing the most consistent growth-related response. Somatic indices were not significantly affected. WCE supplementation increased antioxidant enzyme activities and reduced malondialdehyde levels in serum and liver, particularly at moderate inclusion levels. It also increased lysozyme and peroxidase activities, alternative complement activity, phagocytic index, and respiratory burst activity, and modulated selected immune- and antioxidant-related genes in the liver and intestine. Taken together, dietary WCE, particularly at 10 g kg−1 diet, improved growth and feed utilization while supporting antioxidant status and basal innate immune-associated biomarkers during the eight-week feeding trial, without detectable changes in somatic indices. These findings provide a basis for further evaluating WCE as a plant-derived functional additive for Nile tilapia aquafeeds under pathogen-challenge and practical farming conditions.