Effects of Exogenous MDA Supplementation to Diet on Antioxidant Capacity, Immunity and Body Color of Channel Catfish (Ictalurus punctatus)

Malondialdehyde (MDA) is a common oxidation product in deteriorated aquatic feed, which easily induces oxidative damage and quality deterioration in farmed fish, yet its systemic effects on the physiological function and body color of channel catfish (Ictalurus punctatus) remain poorly understood. This study aimed to investigate the influences of dietary exogenous MDA on antioxidant capacity, immune function and body coloration of channel catfish. A 30-day feeding trial was carried out with four dietary MDA levels of 0, 22.3, 44.6 and 66.8 mg/kg. Relevant physiological and pigment indices of skin and muscle were determined. Exogenous MDA significantly increased plasma transaminase levels and tissue MDA content, decreased antioxidant enzyme activities, and altered the transcription of antioxidant and immune-related genes in skin and muscle, causing oxidative stress and immune dysfunction. It also suppressed tyrosinase activity, downregulated melanin-synthesis-related genes, reduced melanin deposition and promoted uranidin accumulation in the two tissues. Collectively, dietary exogenous MDA impairs antioxidant and immune performance, disrupts pigment metabolism, and ultimately leads to body yellowing in channel catfish.