Scientists tested whether two natural supplements could help Nile tilapia fish grow better and fight infections. They added either selenium nanoparticles (tiny selenium particles), pennyroyal essential oil, or both to fish food for eight weeks. The fish that received these supplements grew better, had stronger immune systems, and survived infections better than fish without supplements. The combination of both supplements worked best. This research suggests these natural additives could be a safe way to improve fish farming and help fish stay healthier without using antibiotics.

The Quick Take

  • What they studied: Whether adding two natural supplements (selenium nanoparticles and pennyroyal oil) to fish food would help fish grow better and fight off bacterial infections
  • Who participated: Young Nile tilapia fish (about 6 grams each) divided into 12 tanks with four different diet groups tested for eight weeks
  • Key finding: Fish that received the supplements grew better and had stronger immune systems. When infected with bacteria, supplemented fish had much lower death rates (similar survival across supplement groups) compared to fish without supplements, with the combination treatment showing the best overall results
  • What it means for you: If you work in fish farming, these natural supplements may help your fish stay healthier and grow better without needing antibiotics. However, this research was done in a lab setting with one fish species, so results may differ in real-world fish farms

The Research Details

Researchers divided young tilapia fish into four groups: a control group (no supplements), a group receiving selenium nanoparticles, a group receiving pennyroyal oil, and a group receiving both supplements. All groups were fed their assigned diets for eight weeks. After eight weeks, the scientists deliberately infected all the fish with a harmful bacteria to see how well each group could fight the infection. They then measured many different health markers in the fish’s blood, intestines, and liver to understand how the supplements affected their bodies.

This type of study is called a controlled experiment because the researchers carefully controlled which fish got which treatment and measured specific outcomes. By using multiple tanks for each treatment (three copies of each group), the researchers could see if results were consistent or just happened by chance.

This research approach is important because it lets scientists test whether supplements actually work before recommending them for real fish farms. By deliberately infecting the fish, researchers could see how well the supplements protected them against disease—something that matters a lot to fish farmers. Measuring many different health markers (digestive enzymes, immune proteins, stress hormones, and antioxidants) helps explain exactly how the supplements help fish stay healthy.

The study used a good scientific design with control groups and multiple replicates, which strengthens the findings. The research was published in a peer-reviewed journal, meaning other scientists reviewed it before publication. However, the study was conducted in a controlled lab environment with one fish species, so results might be different in actual fish farms with different conditions. The sample size appears adequate for detecting differences between groups.

What the Results Show

Fish that received pennyroyal oil grew significantly better than fish without supplements, though all groups converted feed into body weight at similar rates. The supplements improved how well the fish’s digestive system worked—fish receiving pennyroyal oil had higher levels of digestive enzymes that break down carbohydrates, fats, and proteins.

When scientists measured the fish’s natural defense systems, they found that all supplemented groups had stronger antioxidant protection (the body’s ability to fight harmful molecules). Fish receiving pennyroyal oil showed the biggest improvements in these protective enzymes. Both supplements reduced harmful molecules called malondialdehyde, which indicates less cellular damage.

Most importantly, when the fish were infected with bacteria, those receiving supplements had much lower death rates compared to the control group. The combination of both supplements together showed the best protection overall. The supplements also helped fish recover better from infection by maintaining healthier stress hormone levels and better immune function.

The supplements improved several other health markers: liver function improved (shown by lower liver damage markers), immune proteins increased in the blood, and the fish’s natural antibacterial defenses (lysozyme and complement system) were stronger. Fish receiving supplements also had lower stress hormone levels both before and after infection. The combination treatment (selenium plus pennyroyal oil) consistently showed the best results across most measurements.

This research builds on previous studies showing that selenium and essential oils can boost immune function in animals. The finding that combining two supplements works better than either one alone is particularly interesting and suggests that different supplements may work through different mechanisms. The results align with other research showing that natural additives can reduce the need for antibiotics in animal farming.

This study was conducted in a controlled laboratory setting with young fish of similar size, so results may not apply exactly to larger fish or different farming conditions. Only one fish species was tested, so these supplements might work differently in other types of fish. The study didn’t test different doses of the supplements, so we don’t know if higher or lower amounts might work better. Real fish farms have different water conditions, stocking densities, and stress levels that could affect how well these supplements work in practice.

The Bottom Line

For fish farmers: Consider supplementing tilapia feed with pennyroyal essential oil (250 mg/kg) or the combination of selenium nanoparticles (1 mg/kg) plus pennyroyal oil to improve growth and disease resistance. The evidence is moderately strong for this specific fish species in controlled conditions. Start with small-scale testing before applying farm-wide. Consult with aquaculture specialists about implementation in your specific farming system.

Fish farmers raising tilapia will find this most relevant. Feed manufacturers developing aquaculture products should consider these findings. Researchers studying disease prevention in aquaculture should review this work. This research is less relevant to people who eat fish, as the supplements are added to fish feed, not fish meat.

Growth improvements appeared within the eight-week feeding period. Disease resistance benefits were measured immediately after infection. Long-term effects beyond eight weeks are unknown and would require additional research.

Want to Apply This Research?

  • If managing a fish farm, track weekly weight gain of fish on supplemented vs. non-supplemented diets, recording average fish weight and feed consumption to calculate growth rate and feed efficiency
  • Implement a feeding schedule that includes the supplement mixture, starting with a small tank trial to monitor fish health indicators (activity level, appetite, visible health) before expanding to larger populations
  • Maintain records of mortality rates, growth metrics, and any disease outbreaks over 8-12 week periods to compare supplemented and non-supplemented groups and identify the optimal supplement combination for your specific farm conditions

This research was conducted on tilapia fish in a laboratory setting and may not directly apply to other fish species or real-world farming conditions. These findings suggest potential benefits but are not a substitute for professional veterinary or aquaculture advice. Before implementing these supplements in commercial operations, consult with aquaculture specialists and verify regulatory approval in your region. Results may vary based on water quality, fish genetics, stocking density, and other farm-specific factors. This research does not constitute medical or nutritional advice for human consumption.