Researchers tested whether a natural plant extract from Bouea macrophylla could protect fish from dangerous bacteria and ammonia poisoning, potentially replacing antibiotics in fish farms. When fish were fed food containing this plant extract, they survived bacterial infections and toxic ammonia exposure much better than fish given standard antibiotic treatments or no treatment at all. The most promising result was that fish receiving the plant extract showed complete survival against bacterial infection, while those on antibiotics had only 60% survival. This discovery could help fish farmers reduce antibiotic use, which is important for preventing antibiotic-resistant bacteria that threaten human health.

The Quick Take

  • What they studied: Whether a natural plant extract could protect koi fish from bacterial infections and ammonia poisoning as well as or better than antibiotics
  • Who participated: Koi carp (a type of ornamental fish) divided into groups receiving different amounts of plant extract, antibiotics, or no treatment
  • Key finding: Fish fed 1% of the plant extract survived bacterial infection 100% of the time, compared to 60% survival with antibiotics. Against ammonia poisoning, the plant extract group had zero deaths while the antibiotic group had 43% deaths and the untreated group had 90% deaths.
  • What it means for you: This research suggests a natural alternative to antibiotics for fish farming could work better than current methods. However, this study was done on one type of fish, so more testing is needed before it can be used widely in the aquaculture industry.

The Research Details

Scientists divided koi fish into several groups and fed them different diets for a set period. Some fish received food mixed with varying amounts (0.5%, 1%, or 1.5%) of a plant extract made from Bouea macrophylla leaves. Other groups received food with doxycycline (a common antibiotic) or regular food with no supplements. After the feeding period, researchers exposed the fish to dangerous bacteria (Enterococcus faecalis) or high levels of ammonia to see which groups would survive best. They also measured liver health markers in the fish’s blood to check for side effects.

The researchers chose this approach because fish farming currently relies heavily on antibiotics to prevent disease, which contributes to a global problem called antibiotic resistance. This happens when bacteria evolve to survive antibiotics, making these medicines less effective for treating human infections. By testing a natural plant extract, the researchers wanted to find an eco-friendly alternative that could protect fish without contributing to this problem.

This type of study is important because it bridges animal health and human health—a concept called “One Health.” The idea is that what happens in fish farms can affect the broader environment and human populations, so finding better alternatives to antibiotics benefits everyone.

This research approach matters because it tests a real-world solution to a serious global problem. Antibiotic overuse in farming is one of the biggest threats to modern medicine. By comparing the plant extract directly against the current standard treatment (antibiotics) and untreated controls, researchers could see whether this natural alternative actually works better. Testing against multiple challenges (bacterial infection and ammonia poisoning) also shows the extract’s versatility.

The study tested multiple doses of the plant extract to find the most effective amount, which is a sign of careful research design. The researchers measured both survival rates and blood markers to check for harmful effects. However, the study doesn’t specify exactly how many fish were used, which makes it harder to judge how reliable the results are. The study was conducted on only one type of fish (koi carp), so results might differ in other fish species used in farming. The researchers themselves note that larger, longer-term studies are needed to confirm these promising initial findings.

What the Results Show

The plant extract proved remarkably effective against bacterial infection. Fish receiving 1% of the extract in their food showed 100% survival when exposed to dangerous bacteria, meaning every single fish survived. This was better than fish given antibiotics (60% survival) and dramatically better than untreated fish (which presumably had much lower survival, though exact numbers weren’t stated for the control group in the bacterial challenge).

Against ammonia poisoning—a common problem in fish farms when water quality declines—the results were even more striking. Fish fed 1% of the plant extract had zero deaths from ammonia exposure. In comparison, fish given antibiotics had a 43% death rate, and untreated fish had a 90% death rate. This suggests the plant extract protects fish from ammonia damage far better than antibiotics do.

When researchers checked the fish’s liver health by measuring a blood enzyme called SGPT, they found an important difference. Fish fed the plant extract maintained normal liver enzyme levels even after ammonia exposure, suggesting their livers weren’t damaged. Fish given antibiotics showed increased liver enzyme levels after ammonia exposure, indicating some liver stress. This is significant because it suggests the plant extract not only helps fish survive but also protects their organs from damage.

In prevention tests where fish were exposed to naturally occurring Vibrio bacteria (another common fish pathogen), fish fed the highest dose of plant extract (1.5%) had 60% survival, matching the performance of antibiotics. This shows the extract works against multiple types of harmful bacteria, not just the one tested in the main challenge. The fact that different doses produced different results (0.5% was less effective than 1%) suggests there’s an optimal amount to use, which is important for practical application.

This research fits into a growing body of work exploring natural alternatives to antibiotics in farming. Many previous studies have tested plant extracts for disease prevention in fish, but few have shown results as strong as these. The fact that the plant extract outperformed antibiotics in some tests is particularly noteworthy and suggests this specific plant may have special properties worth further investigation. However, most previous research on this plant extract has been limited to laboratory studies, so this real-world test on living fish is an important step forward.

The study has several important limitations that readers should understand. First, the exact number of fish tested isn’t clearly stated, making it hard to judge how reliable the results are. Second, the research was conducted only on koi carp, which are ornamental fish, not the species typically raised for food in large aquaculture operations. Results might be different in other fish species. Third, the study was relatively short-term, so we don’t know if the benefits continue over months or years of feeding the extract. Fourth, the researchers didn’t test whether combining the plant extract with other treatments (like probiotics) might work even better. Finally, the study doesn’t provide detailed information about potential side effects or whether the extract could accumulate in fish tissue over time.

The Bottom Line

Based on this research, the plant extract shows promise as a potential antibiotic alternative for fish farming, but it’s too early to recommend widespread use. The evidence is strong for koi carp specifically (confidence level: moderate to high for this species), but much weaker for other fish species (confidence level: low). If you’re involved in fish farming, this research suggests it’s worth monitoring for future developments, but current antibiotics remain the proven standard. Researchers should prioritize testing this extract in commercially important fish species and in larger, longer-term studies before it becomes a standard farming practice.

Fish farmers and aquaculture companies should care about this research because it offers a potential solution to reduce antibiotic use while maintaining fish health. Environmental advocates should care because reducing antibiotics in farming helps protect the environment and human health. Pet fish owners with koi ponds might eventually benefit if this extract becomes available as a supplement. Veterinarians who treat fish should monitor this research. However, people who don’t work with fish farming or fish health don’t need to make any changes based on this single study.

In the study, fish showed protection within days of being exposed to bacteria or ammonia after eating the supplemented food for a set period. However, this doesn’t mean farmers would see results immediately in real-world conditions. It typically takes weeks to months of consistent feeding before fish develop strong disease resistance. Benefits against ammonia exposure appeared more immediate, suggesting the extract works through multiple mechanisms. Long-term benefits and any potential drawbacks would only become clear after months or years of use, which is why larger studies are needed.

Want to Apply This Research?

  • If you manage a fish farm or aquaculture operation, track weekly fish mortality rates and compare them before and after introducing any plant-based supplement. Also monitor water quality parameters (especially ammonia levels) and document any changes in fish behavior or appearance. This data would help you determine if the supplement is actually working in your specific conditions.
  • Start by researching whether this specific plant extract is available commercially for aquaculture use. If considering implementation, begin with a small test group of fish rather than your entire population. Gradually introduce the supplement while maintaining detailed records of fish health, survival rates, and any visible changes. Continue using proven disease prevention practices (good water quality, proper nutrition, quarantine procedures) alongside any new supplement.
  • Establish a long-term monitoring system that tracks fish health metrics weekly or monthly, including survival rates, growth rates, disease incidence, and water quality. Compare these metrics to your baseline data from before introducing the supplement. Keep records for at least 6-12 months to identify patterns and seasonal variations. Document any unexpected changes in fish behavior, appearance, or mortality that might indicate problems. Share your results with other farmers and researchers to contribute to the growing knowledge base about natural alternatives to antibiotics.

This research describes findings from a single study on koi fish and should not be considered definitive medical or veterinary guidance. The study has not yet been validated in large-scale commercial aquaculture settings or in other fish species. Anyone considering using this plant extract for fish farming should consult with a veterinarian experienced in aquaculture and follow all local regulations regarding feed supplements and disease prevention. This research is preliminary and much more testing is needed before this extract could be recommended as a standard replacement for antibiotics in fish farming. The findings are promising but not yet proven safe and effective for widespread use.