A RUDN University biologist and colleagues from Iran and China proved that the natural antioxidant chrysin improves growth and immunity in rainbow trout. It can help improve the health of fish in intensive farming environments. The results were published in Aquaculture Reports.
Newswise — For fish farm owners, the main goal is to increase production intensity. Because of this, fish are often kept in overcrowded tanks. Such unnatural conditions have a bad effect on the health of fish - chronic and acute stress occurs, which impairs growth and immunity. Veterinarians are looking for harmless supplements or drugs that would help cope with these negative consequences. The focus of researchers is on natural drugs that are obtained from plants. A biologist from RUDN University and colleagues from Iran and China discovered that the natural antioxidant chrysin, which is obtained, for example, from honey and propolis, improves the growth and immunity of fish.
“Increased production has resulted in fish being stressed by overcrowding. Chronic and acute stress reduces the growth and immunity of fish. Therefore, it is important to seek out safe and cost-effective strategies that can help mitigate the harmful effects of stress. Several studies have confirmed the beneficial effects of immunostimulants on fish. Natural ingredients are the best-known feed additives for combating stress in aquatic animals. They receive special attention due to their many positive properties, and therefore the search for more effective compounds continues,” Morteza Yousefi, Associate Professor of the RUDN Department of Veterinary Medicine said.
A scientist from RUDN University tested the effectiveness of chrysin on rainbow trout (Oncorhynchus mykiss). The fish were divided into several groups and given food supplemented with chrysin in different concentrations for 56 days - from 0 to 700 milligrams per kilogram. Before and after the experiment, the researchers measured the immunochemical parameters of the fish’s blood and also compared the growth rates of fish from different groups.
Fish that received 300-500 milligrams of chrysin showed faster weight gain and higher immune system activity. Their numbers of red blood cells, leukocytes, and monocytes returned to normal. Scientists also noticed increased activity of antioxidant enzymes.
“Chrysin at 300-500 mg/kg diet in rainbow trout improves growth, immunity, and resistance of fish to crowding stress. In the future, the effect of chrysin on the resistance of fish to stress from transportation can be studied. In addition, it is proposed to conduct further research to evaluate the mechanism of action of chrysin at the molecular level, as well as its protective effect on fish exposed to infections,” Morteza Yousefi, Associate Professor of the RUDNB Department of Veterinary Medicine said.
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