Climate change is causing a rise in global temperatures, which has devastating consequences for aquatic life. Fish, such as Nile tilapia, are especially vulnerable to these changes in their habitat. Thermal stress caused by rising water temperatures can negatively affect their growth, immunity, and overall well-being.
Previous studies have shown that elevated temperatures can negatively impact the health and performance of tilapia. A decrease in growth, hematological problems, a weakened immune system, and alterations in the general physiology of the fish have been observed. These adverse effects can result in significant economic losses for fish farmers.
Researchers from Bangladesh Agricultural University, Chattogram Veterinary and Animal Sciences University, Pukyong National University, and King Saud University published a study in the journal Animal Feed Science and Technology where they used multi-species probiotics consisting of Bacillus subtilis (5×109 cfu/ml), B. thuringiensis (4×109 cfu/ml), Lactobacillus plantarum (5.8×109 cfu/ml), and L. buchneri (6.5×109 cfu/ml) in rearing water (1.0 ml/l) to mitigate the effects of high temperatures on growth retardation, stress, and immunity of Nile tilapia (Oreochromis niloticus).
Impact of Global Warming on Aquaculture
Global warming is a major concern for aquaculture, as higher water temperatures are expected to have disastrous impacts on both wild and farmed fish species in the near future. Thermal stress disrupts the intestinal microbial community, digestive enzyme activities, immunity and intestinal structure, blood molecules, and functional behavior, resulting in poor production rates and a higher likelihood of infections by pathogenic and opportunistic microbes.
Studies have shown that extreme temperature increases alter gill morphology and oxygen consumption, cause abnormalities in erythrocyte cells and nuclei, and affect growth and hemato-biochemistry in Nile tilapia.
Probiotics: A Promising Solution
In light of this scenario, probiotics emerge as a promising strategy to mitigate the effects of global warming on tilapia. These beneficial microorganisms have shown their ability to improve intestinal health, strengthen the immune system, and optimize digestion in various aquaculture species.
Recent research suggests that probiotics can play a crucial role in protecting tilapia from thermal stress. By balancing the gut microbiota, these microorganisms can help fish better withstand adverse conditions and maintain an effective immune response.
Despite advances in the use of probiotics to mitigate the effects of thermal stress in aquaculture, not enough research has been conducted to identify and quantify the efficiency of multiple probiotics in reducing thermal stress in Nile tilapia. Thus, there is a need to investigate the potential of probiotics to improve growth and immune responses under high temperatures, observing growth parameters, blood erythrocytes, biochemical parameters, intestinal histology, and the expression of genes related to antioxidant and immune responses in Nile tilapia.
Study Results
The researchers demonstrated that supplementation with a combination of beneficial bacteria, including Bacillus subtilis, B. thuringiensis, Lactobacillus plantarum, and L. buchneri, can significantly improve the health and growth of these fish under high-temperature conditions.
The experiment involved rearing tilapia at different temperatures (normal, 31°C; elevated, 34°C, and 37°C) with and without the addition of probiotics for six weeks. The results were surprising:
- Growth: Fish reared at 37°C experienced a significant reduction in growth, but those that received probiotics showed a notable improvement compared to those that were not supplemented.
- Health: Probiotics helped maintain healthy levels of hemoglobin and red blood cells while reducing levels of white blood cells and glucose. Additionally, a decrease in blood cell abnormalities was observed.
- Immunity: Fish treated with probiotics showed a stronger immune response, with higher levels of certain proteins related to the body’s defense.
- Intestinal Health: Probiotics also had a positive impact on the intestinal health of the fish, improving the structure and function of intestinal tissue.
Conclusion
“The findings of this study demonstrated that high temperatures beyond the optimal level cause restrictions in growth and feed utilization in Nile tilapia. However, the application of probiotics substantially reduces stress and growth retardation by improving the physio-immunological properties of Nile tilapia at extremely high temperatures,” the researchers conclude.
These findings have important implications for sustainable aquaculture. The incorporation of probiotics in tilapia farming systems can help protect these fish from the effects of global warming and ensure more efficient and healthier production.
The study was funded by the Krishi Gobeshona Foundation (KGF), Bangladesh Agricultural Research Council, Dhaka, Bangladesh, and Researchers Supporting Project (RSP), King Saud University.
Contact
Md Shahjahan
Laboratory of Fish Ecophysiology, Department of Fisheries Management, Bangladesh Agricultural University
Mymensingh 2202, Bangladesh
Email: mdshahjahan@bau.edu.bd
Reference
Hossain, M. K., Naziat, A., Atikullah, M., Hasan, M. T., Ferdous, Z., Paray, B. A., Zahangir, M. M., & Shahjahan, M. (2024). Probiotics relieve growth retardation and stress by upgrading immunity in Nile tilapia (Oreochromis niloticus) during high temperature events. Animal Feed Science and Technology, 316, 116054. https://doi.org/10.1016/j.anifeedsci.2024.116054
