Dietary Portulaca oleracea Improves Growth Performance, Antioxidant Capacity, andMuscle Quality in Largemouth Bass Fed a High-Fat Diet

High-fat diets are commonly used in aquaculture to reduce dietary protein consumption and feed costs; however, excessive lipid intake may impair fish growth, health status, and flesh quality. This study evaluated the effects of Portulaca oleracea as a functional green feed additive on largemouth bass (Micropterus salmoides) fed a high-fat diet. Fish were fed a control diet, a high-fat diet, or high-fat diets supplemented with different levels of P. oleracea. Growth performance, feed utilization, antioxidant enzyme activities, muscle texture, water-holding capacity, muscle fiber morphology, amino acid composition, and fatty acid composition were analyzed. The results showed that 2% P. oleracea supplementation produced the most beneficial effects. At this level, the specific growth rate increased and feed utilization was improved. In addition, dietary P. oleracea enhanced antioxidant capacity, as indicated by increased SOD and CAT activities in serum and muscle, suggesting improved resistance to oxidative stress induced by high-fat feeding. Furthermore, P. oleracea supplementation improved multiple flesh quality parameters, including reduced drip loss, enhanced texture characteristics, increased muscle fiber density, elevated contents of flavor-related amino acids such as aspartic acid and alanine, and optimized muscle fatty acid composition. These findings suggest that P. oleracea has potential as a functional green feed additive to improve growth performance, antioxidant status, and muscle quality in largemouth bass fed a high-fat diet.