Assessing the effects of Guiera senegalensis, Pluchea odorata, and Piliostigma reticulatum leaf powder supplementation on growth, immune response, digestive histology, and survival of Nile tilapia (Oreochromis niloticus Linnaeus, 1758) juveniles before and after Aeromonas hydrophila infection

This study investigated the effects of including leaf powder from three medicinal plants collected in Senegal in the feeds of juvenile Nile tilapia ( Oreochromis niloticus ) on growth, survival, immunity, and digestive histology. Four experiments were conducted in triplicate, testing each plant alone or in combination at different inclusion levels: A) Guiera senegalensis at 0, 1, 2, 4 and 8%; B) Pluchea odorata at 0, 0.5, 1, 2 and 4%; C) Piliostigma reticulatum at 0, 1 and 2%; and D) a mixture of the three plants at 0, 1 and 2% per plant. After 28 days of feeding, fish underwent an experimental infection with Aeromonas hydrophila for 12 days. Immunological (bactericidal, lysozyme, and respiratory burst activities) and digestive histology analyses were performed following both feeding and infection trials. Except for G. senegalensis , the inclusion of medicinal plants, either alone or in combination, positively influenced the immune response at all inclusion levels. The diet containing 4% P. odorata increased plasma lysozyme and bactericidal activities without compromising feed conversion efficiency or growth. Despite the observed improvements in immunity, none of the dietary treatments enhanced survival following the infection. However, fish fed the 1% mixture diet exhibited healthier livers and intestines, characterized by reduced cell swelling and normal lipid deposits appearance, followed by the 2% mixture and the control groups. These results highlight the potential benefits of incorporating P. odorata and the plant mixture in the diets of Nile tilapia juveniles for enhancing their immune response and defense against A. hydrophila infections.