Dietary Administration of Karonda (Carissa carandas) on the Growth, Digestive Enzymes, Skin Mucosal Immunity, and Pigmentation in Siamese Fighting Fish (Betta splendens)

Karonda (Carissa carandas) fruit contains natural colorants; however, no research has investigated its effects on fish growth and coloration. Thus, this study examined the impacts of C. carandas fruit powder (CCFP) on growth, skin mucosal immunity, digestive enzymes, and pigmentation in Siamese fighting fish (Betta splendens). Flavonoids (15.97 ± 0.48 mg quercetin equivalent/g CCFP), phenolics (43.52 ± 1.73 mg gallic acid equivalent/g CCFP), terpenoids (350.00 ± 15.66 mg linalool equivalent/g CCFP), tannins (40.97 ± 0.15 mg tannic acid equivalent/g CCFP), carotenoids (5.53 ± 0.73 µg/g CCFP), and β-carotene (0.67 ± 0.05 µg/g CCFP) were estimated in CCFP. In the 2,2-diphenyl-1-picrylhydrazyl assay, CCFP showed antioxidant activity with an IC50 of 256.12 ± 7.68 μg/ml. Fish (0.42 ± 0.02 g weight and 3.20 ± 0.07 cm length) were fed diets containing CCFP at 0 (control), 3, 6, and 9 g/kg for 8 weeks. The results showed that CCFP administration significantly enhanced final weight, length, weight gain, specific growth rate, and average daily gain (p < 0.05). No changes in feed conversion ratio, survival, and condition factor were observed (p > 0.05). Dietary CCFP significantly increased skin mucus lysozyme, alkaline phosphatase, IgM, myeloperoxidase, total protein, antioxidant capacity, catalase, and superoxide dismutase. Fish treated with CCFP showed significant increases in intestinal protease, lipase, and amylase activity, as well as skin, muscle, and fin carotenoid levels. In conclusion, the administration of CCFP at 9 g/kg is optimal for improving growth, digestive enzymes, skin mucosal immunity, and pigmentation in B. splendens.