Antibiotics have played a crucial role in aquaculture, but their excessive use has led to antibiotic resistance in bacteria. This poses a significant threat to fish health and human safety.
Researchers from Guangdong Ocean University, Yunnan Agricultural University, and Tongwei Agricultural Development Co., Ltd. are exploring alternatives, and a new study is investigating the potential of palmatine, a plant extract with antibacterial properties, as a dietary supplement for tilapia.
They evaluated the feasibility of palmatine as an antibiotic alternative in the diet of genetically improved farmed tilapia (GIFT, Oreochromis niloticus).
Antibiotics: a double-edged sword
Many aquaculturists have turned to antibiotics like enrofloxacin and tetracyclines as a solution. While these drugs can control infections, their overuse has a dark side. Antibiotic residues can linger in water and fish, potentially harming human health by promoting antibiotic resistance in harmful bacteria.
So, what’s the solution?
Fortunately, researchers are exploring natural alternatives to antibiotics that can boost tilapia’s immune system and fight infections. This is where plant-based immunostimulants come into play.
Several plant extracts such as Thai ginseng, lemon peel, and berberine have shown promise in tilapia feeding. These natural ingredients enhance the fish’s immune response, making them more resistant to diseases.
Palmatine: a promising natural antibacterial
Palmatine, an extract from plants like berberine or Coptis chinensis, has been well-studied for its health benefits in humans and is gaining attention for its potential in tilapia aquaculture. This natural compound boasts several impressive properties:
- Antioxidant power: Palmatine helps combat free radicals, protecting tilapia cells from damage.
- Antimicrobial warrior: Studies suggest that palmatine can effectively fight Aeromonas hydrophila, a significant tilapia pathogen.
- Immune system booster: Research indicates that palmatine can strengthen tilapia’s innate immune system, better preparing it to fight infections.
The impact of palmatine on tilapia
This study aimed to evaluate its effectiveness as an antibiotic alternative in the diet of genetically improved farmed tilapia (GIFT).
The research involved feeding tilapia diets containing different levels of palmatine (0, 200, 400, and 800 mg/kg) for ten weeks. Here’s a breakdown of the key findings:
- Unaffected growth: Regardless of the palmatine level, fish growth and feed efficiency remained constant.
- Improved cholesterol profile: Diets containing 200 mg/kg or more of palmatine effectively reduced total and “bad” (LDL) cholesterol levels in tilapia. Additionally, it improved the ratio between LDL and “good” (HDL) cholesterol.
- Enhanced antioxidant activity: Palmatine supplementation at all levels generally increased the activity of antioxidant enzymes in the intestine, blood plasma, and liver.
- Strengthened immune system: The study observed a positive impact on various markers of the immune system. Fish fed palmatine diets showed elevated levels of immunoglobulin M, complement proteins (C3 and C4), and lysozyme activity, all indicative of a stronger immune response. Phagocytic activity, the ability of immune cells to engulf and destroy bacteria, also improved in fish.
- Increased disease resistance: Fish fed palmatine-supplemented diets, particularly those with 400 mg/kg, demonstrated a significant increase in resistance to Aeromonas hydrophila, a common bacterial pathogen in aquaculture.
The study highlights the potential of palmatine as a viable alternative to antibiotics in tilapia farming. Its ability to enhance the immune system and disease resistance while maintaining healthy growth and cholesterol levels is particularly encouraging.
Optimal inclusion level
According to the findings, the optimal dietary inclusion level of palmatine for tilapia appears to be 400 mg/kg. This level effectively improved disease resistance without compromising growth.
Conclusion
This study paves the way for the use of natural plant extracts like palmatine as an alternative to antibiotics in tilapia aquaculture.
Further research is needed to explore the long-term effects of palmatine on tilapia health and the environment. However, these initial findings lay the groundwork for a more sustainable and responsible approach to tilapia aquaculture, potentially reducing antibiotic dependence and promoting healthier fish.
The study was funded by the National Natural Science Foundation of China; the Program for Scientific Research Start-up Funds of Guangdong Ocean University; the Special Project in Key Fields of Universities in Guangdong Province; the Zhanjiang Innovation and Entrepreneurship Team Cultivation “Pilot Program” Project; and the Foundation of Tongwei Co., Ltd.
Contact
Haifeng Mi
Tongwei Agricultural Development Co., Ltd.
Chengdu 610093, China
Email: mihaifengtw@163.com
Junming Deng
College of Fisheries, Guangdong Ocean University
Zhanjiang 524088, China.
Email: djunming@163.com
Reference (open access)
Fu, X., Li, Y., Zhang, L., Mi, H., & Deng, J. (2024). Evaluation of palmatine as an immunostimulant in diet for genetically improved farmed tilapia (GIFT, Oreochromis niloticus). Aquaculture Reports, 35, 102001. https://doi.org/10.1016/j.aqrep.2024.102001
