Dietary Fermented Pineapple Pomace Improves Intestinal Health and Antioxidant Capacity Without Compromising Growth Performance in Juvenile Largemouth Bass (Micropterus salmoides)

This study evaluated the influence of dietary fermented pineapple pomace (FPP) supplementation on growth performance, intestinal health, and antioxidant capacity in juvenile largemouth bass (Micropterus salmoides). Six experimental diets containing 0%, 2%, 4%, 6%, 8%, and 10% FPP were formulated and fed for 10 weeks, with FPP replacing equivalent proportions of wheat flour in the basal diet. The results showed that dietary FPP did not impair the growth performance of largemouth bass. The FP4 and FP6 diets significantly increased the villus height, whereas the FP4, FP6, and FP8 diets significantly increased the villus width. Dietary FPP also enhanced several intestinal digestive and absorptive enzyme activities, including lipase, amylase, trypsin, lactase, and alkaline phosphatase, although the responsive inclusion levels differed among enzymes. Dietary FPP generally reduced intestinal mucosal permeability, alleviated barrier damage, and enhanced mucosal barrier integrity. In addition, FPP supplementation improved intestinal chemical and immune barrier function, as reflected by increased lysozyme activity, mucin 2 level, secretory immunoglobulin T level, and immunoglobulin M level at appropriate inclusion levels. Dietary FPP improved antioxidant status by increasing serum catalase activity and total antioxidant capacity at appropriate inclusion levels, while low-level FPP supplementation increased the serum superoxide dismutase activity and decreased the serum malondialdehyde level. Overall, replacing wheat flour with dietary FPP did not impair growth performance and improved intestinal digestive and absorptive functions, mucosal barrier integrity, and antioxidant capacity. Therefore, 4–6% may be considered a favorable dietary inclusion range for FPP in largemouth bass feed under the present experimental conditions. Because an unfermented pineapple pomace comparison group was not included, these effects should be interpreted as the effects of dietary FPP as a whole rather than as fermentation-specific effects.