A Gram Research analysis of 160 weaned piglets found that supplementing feed with 2 grams per kilogram of chestnut-quebracho tannins reduced diarrhea by 32% at day 49 on one farm, though growth performance was unchanged. The tannins worked by changing gut bacteria composition and being converted into bioactive compounds called urolithins, suggesting benefits depend on a piglet’s existing bacterial community. Results varied between farms, indicating that tannin effectiveness depends on farm-specific conditions.
Researchers tested whether tannins from chestnuts and quebracho trees could improve gut health in young piglets after weaning. In a study of 160 piglets across two farms, those fed a diet with added tannins had less diarrhea and different gut bacteria compared to piglets on a regular diet. The tannins worked by changing how gut bacteria break down plant compounds into helpful molecules called urolithins. While the tannins didn’t make piglets grow faster, they did reduce digestive problems, especially on one farm. This research suggests that plant-based supplements might help young animals stay healthier during stressful transitions like weaning.
Key Statistics
A 2026 study of 160 weaned piglets found that chestnut-quebracho tannin supplementation at 2 grams per kilogram of feed reduced diarrhea occurrence by 32% at day 49 on one commercial farm, though the effect was not consistent across both farms tested.
According to research reviewed by Gram, tannin-treated piglets showed higher levels of beneficial bacteria including Megasphaera elsdenii, Faecalibacterium prausnitzii, and Lactobacillus amylovorus, while control piglets had higher levels of potentially harmful Escherichia coli.
A 2026 analysis of 160 piglets across two farms identified three different urolithin metabotypes (bacterial conversion patterns), with 50% of tannin-treated samples showing one particular pattern, indicating variable bacterial capacity to convert tannins into bioactive compounds.
Tannin supplementation did not affect overall growth performance in weaned piglets over 76 days, suggesting that benefits are limited to digestive health rather than improved feed efficiency or weight gain.
The Quick Take
- What they studied: Whether a blend of tannins from chestnuts and quebracho trees could improve gut health, reduce diarrhea, and change the bacteria living in the digestive systems of young piglets after weaning.
- Who participated: 160 weaned piglets weighing about 6.5 kilograms at the start, raised on two different commercial farms. Half received a regular diet, and half received the same diet plus 2 grams of tannin blend per kilogram of feed for 76 days.
- Key finding: Tannin supplementation reduced diarrhea occurrence by 32% at day 49 on one farm (W2), and changed the types and amounts of bacteria in piglet feces. The tannins were converted by gut bacteria into beneficial compounds called urolithins, which appeared in higher amounts in treated piglets.
- What it means for you: For pig farmers, this suggests that adding plant tannins to piglet feed might reduce digestive problems during the vulnerable weaning period, though benefits appear to depend on farm conditions. The effect is modest but could reduce antibiotic use and improve animal welfare. More research is needed to confirm these findings apply broadly.
The Research Details
Researchers divided 160 weaned piglets into four groups based on which of two farms they lived on and which diet they received. One group got regular feed, while the other got the same feed plus a blend of tannins from chestnuts and quebracho trees. The study lasted 76 days, with measurements taken at four time points: when piglets arrived, at day 35, day 49, and day 76. Scientists collected fecal samples (poop samples) to analyze the bacteria living in each piglet’s gut using DNA sequencing and to measure chemical compounds produced by those bacteria. They also tracked diarrhea occurrence and weighed the piglets regularly to see if growth was affected.
This design is called a factorial experiment because it tests two factors at once: the farm location and the dietary treatment. By testing on two different farms, researchers could see whether the tannin effects worked the same way everywhere or depended on farm-specific conditions like different bacteria already present or different management practices.
The researchers used advanced laboratory techniques to identify which bacteria were present and which chemical compounds appeared in the fecal samples. They specifically looked for urolithins, which are compounds created when gut bacteria break down tannins. This allowed them to understand not just whether tannins worked, but how they worked through the bacteria.
This research approach matters because it goes beyond simply measuring whether piglets got sick or grew well. By analyzing the actual bacteria and chemical compounds in the gut, researchers could understand the mechanism: how tannins work through the bacteria to create beneficial effects. This is important because it shows that tannin effectiveness depends on whether a piglet’s gut bacteria can convert tannins into active compounds. Understanding this mechanism helps predict which piglets or farms might benefit most from tannin supplementation.
The study has several strengths: it included a reasonable number of piglets (160), used two different farm environments to test whether results generalize, collected samples at multiple time points to track changes over time, and used rigorous laboratory methods to identify bacteria and chemical compounds. However, the study has limitations: it was conducted only on pigs, so results may not apply to other animals or humans; the diarrhea reduction was modest and only appeared on one farm; growth performance was not improved; and the study is correlative, meaning it shows which bacteria and compounds are associated with tannin treatment but doesn’t prove they cause the benefits. The researchers themselves note that the microbial partnerships they identified need further testing to confirm they actually cause the effects.
What the Results Show
Tannin supplementation did not increase how fast piglets grew or how much weight they gained over the 76-day study period. However, tannins did reduce diarrhea occurrence at day 49, but only on one of the two farms (farm W2, with a 32% reduction). This suggests that tannin effectiveness may depend on farm-specific conditions.
The most striking findings came from analyzing gut bacteria and chemical compounds. Tannin-treated piglets had different bacterial communities compared to control piglets, with consistent differences across all three sampling time points. Specifically, tannin-treated piglets had higher levels of bacteria like Megasphaera elsdenii, Faecalibacterium prausnitzii, and Lactobacillus amylovorus, which are considered beneficial. Control piglets had higher levels of Escherichia coli, a bacteria that can cause digestive problems.
When researchers analyzed the chemical compounds in fecal samples, they found that tannin-treated piglets produced higher amounts of urolithins, which are bioactive compounds created when gut bacteria break down tannins. These compounds were especially abundant in piglets from farm W2. The researchers identified three different urolithin patterns (metabotypes) among the piglets, with 50% showing one particular pattern. This variation suggests that different piglets’ bacteria convert tannins differently, which may explain why benefits varied between farms.
The study found that farm location was a major driver of bacterial diversity early after weaning, suggesting that farm-specific factors like management practices, feed sources, or existing bacteria strongly influence the gut microbiota. However, tannin treatment consistently changed bacterial composition across both farms, indicating that tannins have a real effect even when farm conditions differ. The researchers identified specific bacterial species that work together to produce urolithins, suggesting that tannin benefits depend on having the right combination of bacteria present. Isourolithin A and urolithin B were the most distinctive compounds in tannin-treated piglets, particularly in farm W2, suggesting these may be the active compounds responsible for health benefits.
This research builds on earlier studies suggesting that tannins can improve gut health in young animals. Previous research has shown that tannins have antimicrobial properties and can reduce harmful bacteria. This study goes further by showing that tannins work partly by changing which bacteria thrive in the gut and by being converted into new compounds (urolithins) that may have their own health benefits. The finding that benefits depend on farm conditions is important because it explains why some previous studies found strong effects while others found weak effects. This research also aligns with growing interest in using plant compounds instead of antibiotics to keep young animals healthy during vulnerable periods like weaning.
The study has several important limitations. First, it only measured associations between tannins, bacteria, and urolithins, not proof of cause and effect. The bacteria identified may be markers of tannin effects rather than the actual cause of benefits. Second, the diarrhea reduction was modest and only appeared on one farm, raising questions about how broadly these results apply. Third, growth performance was not improved, so farmers might not see economic benefits even if diarrhea decreases. Fourth, the study was conducted only in pigs, so results cannot be assumed to apply to other animals or humans. Fifth, the study lasted only 76 days, so long-term effects are unknown. Finally, the researchers note that the microbial partnerships they identified are correlative and need functional validation, meaning laboratory experiments are needed to prove these bacteria actually cause the effects.
The Bottom Line
Based on moderate evidence, chestnut-quebracho tannin supplementation at 2 grams per kilogram of feed may reduce post-weaning diarrhea in piglets, particularly in certain farm environments. However, the effect is modest and does not improve growth performance. Farmers considering this approach should: test it on their specific farm before widespread adoption, monitor diarrhea rates and gut health indicators, and recognize that results may vary depending on existing farm conditions and the bacteria already present. This approach may be most valuable as part of a strategy to reduce antibiotic use rather than as a growth promoter.
Pig farmers and veterinarians managing weaned piglets should pay attention to this research, especially those looking to reduce antibiotic use or manage digestive problems during weaning. The findings are most relevant to commercial pig operations with similar conditions to the farms studied. Pet owners, parents, and people interested in human nutrition should note that this research is specific to pigs and does not yet have proven applications to other species. Researchers studying gut bacteria and plant compounds will find value in the methodology and findings about how bacteria convert tannins into bioactive compounds.
If tannins are effective on a particular farm, benefits would likely appear within 2 to 3 weeks of starting supplementation, based on the timing of reduced diarrhea in this study (day 49, or about 7 weeks into the weaning period). However, changes to gut bacteria composition may take several weeks to develop fully. Farmers should expect modest effects rather than dramatic improvements and should monitor results over at least one full weaning cycle before deciding whether to continue supplementation.
Frequently Asked Questions
Do tannins help prevent diarrhea in young piglets after weaning?
Research shows tannins reduced diarrhea by 32% in one farm setting, but effects were inconsistent across farms. Benefits appear to depend on existing farm conditions and gut bacteria composition, so results may vary by location.
How do plant tannins improve gut health in animals?
Tannins work by changing which bacteria thrive in the gut and being converted by those bacteria into bioactive compounds called urolithins. This process shifts the bacterial community toward beneficial species like Faecalibacterium prausnitzii.
Will tannin supplements make piglets grow faster or bigger?
No. A 2026 study of 160 piglets found that tannin supplementation did not affect growth performance or weight gain over 76 days, suggesting benefits are limited to digestive health rather than improved growth.
Can tannin supplements replace antibiotics in pig farming?
Tannins may reduce diarrhea and could help decrease antibiotic use, but they are not a complete replacement. The modest effects suggest tannins work best as part of a broader strategy to maintain gut health during weaning.
Why do tannin benefits vary between different farms?
Farm-specific conditions like existing bacteria, management practices, and feed sources strongly influence whether tannins effectively reduce diarrhea. Piglets need the right bacterial species present to convert tannins into active compounds.
Want to Apply This Research?
- Track daily diarrhea occurrence and severity in weaned piglets on a 0-3 scale (0 = normal feces, 3 = severe diarrhea) for at least 8 weeks. Record which piglets received tannin supplementation and compare diarrhea rates between groups. Also track feed intake and weight gain to monitor whether tannins affect overall performance.
- Implement tannin supplementation at 2 grams per kilogram of feed starting at weaning. Maintain detailed records of which batches of piglets receive the supplement, farm conditions, and health outcomes. Use the app to set reminders for fecal sample collection and health assessments at regular intervals (weekly or bi-weekly) to track changes over time.
- Create a long-term tracking system that compares diarrhea rates, antibiotic use, and growth performance between piglets receiving tannin supplementation and control groups across multiple weaning cycles. Monitor whether benefits remain consistent or change with seasonal variations, feed sources, or other farm management changes. Track which farms or conditions show the strongest response to help predict when tannin supplementation will be most effective.
This research describes effects of tannin supplementation in piglets under specific farm conditions and should not be interpreted as medical advice for humans or other animals. The study shows associations between tannins, bacteria, and reduced diarrhea but does not prove causation. Results varied between farms, suggesting effectiveness depends on local conditions. Anyone considering tannin supplementation for animals should consult with a veterinarian. This research has not been tested in humans and should not be used to guide human dietary choices without additional human-specific research.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.