AUTHOR=Fadel Amr , Metwally Mohamed M. M. , Hassan Habib Ul , Abdelmageed Adel A. , Arai Takaomi , Ahmed Mohammad Z. , Abdel-Aziz Mohamed F. A. 

TITLE=Growth, immunomodulatory, histopathological, and antibacterial effects of phytobiotic-incorporated diets on Oreochromis niloticus in unchanged water

JOURNAL=Frontiers in Marine Science

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2024.1473053

DOI=10.3389/fmars.2024.1473053

ISSN=2296-7745

ABSTRACT=<p>Phytobiotics are promising diet alternatives, yet their effectiveness in high-risk aquaculture conditions remains underexplored. Therefore, a 90-day feeding trial was conducted based on dietary supplementation of Nile tilapia, <italic>Oreochromis niloticus</italic>, with herbal extracts, namely, lemon balm [<italic>Melissa officinalis</italic> (MOE)], marjoram [<italic>Origanum majorana</italic> (OME)], and chamomile [<italic>Matricaria chamomilla</italic> (MCE)] with 0% water change. The treated groups were compared to groups untreated with herbs or control groups [positive control (PC; 0% water change) and negative control (NC; 20% water exchange per day]. Fish were cultured at stocking density (20 fish m<sup>-3</sup>: 1.8kg of biomass/m3). We conducted a physicochemical analysis of the water and the clinical responses, growth, and immune responses of the fish were evaluated. Furthermore, the herbal-supplemented fish were then challenged with a pathogenic <italic>Edwardseilla tarda</italic> strain and mortality was monitored. In the 1<sup>st</sup> and 2<sup>nd</sup> months, the water parameters were within the permissible limits. After that, a fatally low dissolved oxygen concentration and the highest levels of ammonia, nitrite, nitrate, and pH were recorded during the 3<sup>rd</sup> month. Blood and immune assays were conducted in the treated groups and control groups. The herbal-treated groups appeared healthy, but during the 3rd month, lethargy and decreased appetite were evident. Generally, the herbal-treated fish showed improved growth performance parameters, survival rates, and resistance against pathogenic bacteria <italic>E. tarda</italic>, particularly in the OME and MOE-treated groups compared to the positive control group. Finally, phytobiotic supplements were shown to improve fish stress tolerance and immune activation for a certain period under stressful conditions or unchanged water, based on the stocking density, dosages of herbs used, and the extent of deterioration of the water quality.</p>