Newswise — RUDN biologists with colleagues from Iran and Ireland have found a plant extract that will help fish in aquaculture to more easily survive the rise in temperature due to global warming. Results published in Frontiers in Veterinary science.
An increase in temperature in artificial reservoirs causes thermal stress in fish. The body temperature of fish is approximately equal to the environment and rises with it, which changes the molecular processes in the body and leads to thermal stress. This reduces the efficiency of fish farms and thus creates stress. RUDN University Biologist with colleagues from Iran and Ireland found that hyssop extract, a subshrub similar to mint, can mitigate thermal stress.
“Global warming is causing problems in various aquaculture sectors. Especially in the cultivation of cold-water species - for example, trout. Fish change their temperature depending on the external environment, so they are very sensitive to fluctuations in water temperature. Due to thermal stress, disturbances in oxygen consumption, metabolism, growth, and reproduction can occur. Therefore, it is necessary to find methods that suppress the adverse effects of thermal stress,” said Morteza Yousefi, Associate Professor, Department of Veterinary Medicine, RUDN University.
Biologists studied the effect of the additive on 144 rainbow trout fry. The fry were divided into four groups, each of which received, along with the usual feed, an additive of hyssop in different concentrations - from 0 to 500 milligrams per kilogram. For 62 days, the fish lived in an environment with a temperature of 13.3 ℃ - normal for this species , and then another week at a temperature of 21-22 ℃. After the end of the experiment, RUDN University biologists measured the level of enzymes in the blood and other health indicators.
The addition of hyssop to the feed had no effect on fish growth, feed digestibility or survival. However, the molecular parameters of the blood have changed. So, 250 mg of hyssop reduced the activity of alanine aminotransferase, an enzyme that is involved in protein metabolism. This suggests that it was easier for the fish to tolerate stress due to the increase in temperature. In terms of the sum of other changes in blood plasma, it was 250 mg/kg that turned out to be the optimal amount that helps fish cope with stress.
“Based on our results, we can recommend the addition of hyssop in the amount of 250 mg/kg to the usual feed to improve antioxidant responses and protection in rainbow trout under conditions of heat stress,” Morteza Yousefi, Associate Professor of the Department of Veterinary Medicine, RUDN University.
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