Dietary bioactive compounds poly-β-hydroxybutyrate, mannan oligosaccharide, and inulin affected the growth performance, gut microbiota, and body composition of African catfish (Clarias gariepinus, Burchell, 1822) larvae

High mortality rates and sub-optimal growth performance during the early larval stage of African catfish ( Clarias gariepinus ) larviculture remain significant challenges, limiting its aquaculture in Ethiopia. In this study, the effects of three prebiotics, Mannan Oligosaccharide (MOS), Inulin, and Poly-β-hydroxybutyrate (PHB) on growth performance, survival, gut microbiota, and body composition of African catfish larvae were evaluated. Results showed that PHB supplementation significantly enhanced survival rate (88.89 % ± 3.85 %), final weight (4.20 ± 1.128 g), final length (7.51 ± 0.406 cm), specific growth rate (4.08 ± 0.470 g/day), and daily weight gain (0.06 ± 0.0 g/day) compared to control and other prebiotic-treated groups. On the other hand, MOS and Inulin supplementation did not yield significant improvements in growth parameters compared to the control. Prebiotics supplementation did not affect whole-body proximate composition (P > 0.05). In terms of microbial composition, PHB (1.46×10 7 ±6.81×10 5 CFU/mL) and MOS (1.45×10 7 ±4.04×10 5 CFU/mL) showed significantly lower TBC. LAB abundance was highest in MOS (3.00×10 2 ±1.73×10 2 CFU/mL) and PHB (2.65×10 2 ±1.53 ×10 2 CFU/mL) supplemented groups, whereas Inulin supplementation favored lower LAB growth of 3.00×10 2 ±1.73×10 2 CFU/mL. There was no LAB growth in the intestines of the control group in this experiment. Total Bacillus count was highest in the PHB (2.67×10 4 ±2.52×10 2 CFU/mL) supplemented groups of fish, followed by Inulin (1.83×10 4 ±5.29×10 2 CFU/mL) and MOS (1.48×10 4 ±2.52×10 2 CFU/mL). In contrast, the control (1.28×10 4 ±3.06×10 2 CFU/mL) group exhibited the lowest presence of Bacillus bacteria. In conclusion, dietary prebiotic supplementation influenced growth performance, survival, and gut microbiota in African catfish larvae, with PHB demonstrating the most substantial benefits.