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Lieke T, Steinberg CEW, Pan B, Perminova IV, Meinelt T, Knopf K, Kloas W. Phenol-rich fulvic acid as a water additive enhances growth, reduces stress, and stimulates the immune system of fish in aquaculture. Sci Rep 2021; 11:174. [PMID: 33420170 PMCID: PMC7794407 DOI: 10.1038/s41598-020-80449-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 12/21/2020] [Indexed: 02/07/2023] Open
Abstract
Aquaculture has become imperative to cover the demands for dietary animal protein. Simultaneously, it has to overcome prejudices from excessive use of antibiotics and environmental impacts. Natural supplements are traditionally applied orally. In this study, we demonstrated another pathway: the gills. Humic substances are immunostimulants and a natural part of every aquatic ecosystem, making them ideal to be used as bath stimulants. Five and 50 mg C/L of a fulvic acid-rich humic substance was added for 28 days to the water of juvenile rainbow trout (Oncorhynchus mykiss). This fulvic acid is characterized by a high content of phenolic moieties with persistent free radicals and a high electron exchange capacity. The high concentration of the fulvic acid significantly increased growth and reduced the food conversion ratio and the response to a handling-stressor. Phagocytosis and potential killing activity of head kidney leukocytes were increased, as well as the total oxyradical scavenging capacity (TOSC) and lysozyme activity in the gills. In conclusion, immunostimulation via gills is possible with our fulvic acid, and the high phenolic content improved overall health and stress resistance of fish.
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Affiliation(s)
- Thora Lieke
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, 12587, Germany. .,Faculty of Life Sciences, Humboldt University of Berlin, Berlin, 10115, Germany.
| | - Christian E W Steinberg
- Faculty of Life Sciences, Humboldt University of Berlin, Berlin, 10115, Germany.,Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China
| | - Bo Pan
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China
| | - Irina V Perminova
- Lomonosov Moscow State University, Leninskie Gory, 119991, Moscow, Russia
| | - Thomas Meinelt
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, 12587, Germany
| | - Klaus Knopf
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, 12587, Germany.,Faculty of Life Sciences, Humboldt University of Berlin, Berlin, 10115, Germany
| | - Werner Kloas
- Department of Ecophysiology and Aquaculture, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, 12587, Germany.,Faculty of Life Sciences, Humboldt University of Berlin, Berlin, 10115, Germany
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