Researchers tested whether adding yeast cell wall powder to fish food could help European seabass grow better and handle stressful conditions. Over 9 weeks, fish eating food with the highest amount of this additive grew about 5% larger, ate their food more efficiently, and showed stronger immune defenses in their skin and digestive system. The fish also handled stress from crowding and poor water conditions better than fish eating regular food. The study suggests that this natural food additive could be a practical way to keep farmed fish healthier without using medications.

The Quick Take

  • What they studied: Whether adding different amounts of yeast cell wall (a natural ingredient from baker’s yeast) to fish food would help seabass grow better and stay healthy under stressful conditions
  • Who participated: European seabass fish divided into four groups, each eating food with different amounts of yeast cell wall additive (none, low, medium, or high doses) over 9 weeks
  • Key finding: Fish eating the highest dose of yeast cell wall grew about 5% larger, used their food 8% more efficiently, and showed stronger immune markers in their skin and waste compared to fish eating regular food
  • What it means for you: This research suggests that adding yeast cell wall to farmed fish food could be a natural, safe way to help fish grow better and stay healthier. However, this study was done with one type of fish, so results may differ for other fish species or in different farming conditions.

The Research Details

Scientists divided seabass into four groups and fed each group the same basic diet, but with different amounts of yeast cell wall powder added (0, 1.5, 3.0, or 4.5 kilograms per metric ton of food). The study lasted 9 weeks and was split into two phases: the first 6 weeks were normal conditions, and the last 3 weeks included stressful conditions like overcrowding, low oxygen water, and frequent handling to see how well the fish could cope.

The researchers measured how much the fish grew, how efficiently they converted food into body weight, and checked their immune system markers by examining their skin mucus and fecal samples. They looked for specific immune proteins that indicate how strong the fish’s natural defenses were.

This research approach is important because it tests whether a natural food additive works in real farming conditions, not just in laboratory settings. By gradually increasing the dose and measuring multiple health markers, the scientists could find the best amount to use without wasting money on too much additive. Testing during both normal and stressful periods shows whether the additive actually helps fish when they face real farm challenges.

This is a controlled experiment where all conditions except the yeast additive were kept the same, which is a strong research design. The study measured multiple health indicators rather than just growth, which gives a more complete picture. However, the study doesn’t specify exactly how many fish were tested, and results are specific to one fish species, so findings may not apply equally to other types of fish or farming systems.

What the Results Show

Fish that received the highest dose of yeast cell wall (4.5 kg per metric ton) showed the best results. These fish were about 5% heavier at the end of the first 6-week period compared to fish eating regular food. Throughout the entire 9-week study, fish getting the highest yeast dose grew 5.8% faster and converted their food into body weight 8.3% more efficiently than control fish.

The yeast additive also strengthened the fish’s immune system. Fish eating supplemented food had more immune cells in their intestinal lining, and those eating the highest dose produced 31% more protective mucus on their skin. This mucus acts like a shield against infections and stress.

When researchers examined the fish’s waste, they found interesting patterns. During the first 6 weeks (normal conditions), a stress-related protein called calprotectin increased with higher yeast doses. During the stressful final 3 weeks, this protein decreased in fish eating the yeast additive, suggesting their bodies were handling stress better. Meanwhile, protective mucus proteins in the waste increased steadily with higher yeast doses throughout the entire study.

The study revealed a dose-response relationship, meaning that more yeast additive generally produced better results, but the benefits leveled off around 3.0 to 4.5 kg per metric ton. This suggests there’s an optimal amount to use—adding more than this wouldn’t provide extra benefits. The fish’s ability to handle stress (measured by immune markers) improved most noticeably in the group receiving the highest yeast dose, indicating this additive may be particularly valuable during challenging farm conditions.

Previous research has shown that yeast cell wall can boost fish immunity, but this study is one of the first to carefully test different doses and measure how well it works during actual stressful farming situations. The findings align with what scientists have observed in other fish species and farm animals, supporting the idea that yeast-based additives are a reliable tool for improving animal health across different contexts.

The study focused only on European seabass, so results may not apply to other fish species. The exact number of fish tested wasn’t specified in the available information. The stressful conditions tested (crowding, low oxygen, handling) represent common farm challenges but may not reflect all possible stressors fish face. The study lasted 9 weeks, which is relatively short-term, so we don’t know if benefits continue or change over longer periods. Additionally, the research doesn’t compare yeast cell wall to other health-promoting additives, so it’s unclear whether this is the best option available.

The Bottom Line

Based on this research, fish farmers may consider adding yeast cell wall to seabass feed at doses between 3.0 and 4.5 kg per metric ton to improve growth and health. This recommendation has moderate confidence because it comes from a well-designed study but is limited to one fish species. Farmers should start with these doses and monitor their specific fish populations, as results may vary based on water quality, fish genetics, and other farm conditions.

Fish farmers raising European seabass or similar species should pay attention to these findings, as they offer a practical way to improve fish health without medications. Pet fish owners keeping seabass in aquariums might also benefit from understanding this research, though commercial fish foods may already contain similar additives. This research is less relevant for people who eat fish, as the additive is used during farming and doesn’t remain in the final product.

Fish showed measurable growth improvements within 6 weeks of eating the supplemented food. Immune system improvements appeared gradually over the 9-week study period. In a real farm setting, benefits would likely become noticeable within 4-8 weeks, though the full protective effects during stressful periods may take longer to develop.

Want to Apply This Research?

  • For aquaculture users: Track weekly weight gains and feed conversion ratios (amount of food needed to gain one pound of body weight) for fish groups receiving different yeast additive doses. Record these measurements alongside water quality parameters and stressful events to correlate improvements with the additive level.
  • For fish farmers: Implement a gradual transition to yeast cell wall-supplemented feed at 3.0-4.5 kg per metric ton, monitoring fish growth rates and health indicators weekly. Document any changes in fish behavior, disease resistance, and feed consumption to determine if the additive works well in your specific farming conditions.
  • Establish a baseline of current growth and health metrics before introducing the additive. Then track growth performance, feed efficiency, and visible health signs (skin condition, mucus production, activity levels) monthly. Compare results to your baseline and adjust the additive dose if needed. Keep records of any stressful events (equipment failures, temperature changes, disease exposure) to see whether supplemented fish handle these challenges better than before.

This research describes results from a controlled study on European seabass and should not be considered medical or veterinary advice. Fish farmers should consult with aquaculture specialists or veterinarians before making changes to feed formulations, as results may vary based on fish species, water conditions, and farm-specific factors. This study was conducted on farmed fish and does not provide guidance for treating sick animals or replacing veterinary care. Always follow local regulations regarding feed additives and consult with feed manufacturers about proper supplementation levels.