Gram Research analysis of a 2026 randomized controlled trial found that hazelnut skin extract did not improve recovery from diarrhea in 60 hospitalized dairy calves. Both calves receiving the extract and calves receiving only standard medical treatment recovered at identical rates over five days, with no differences in diarrhea improvement, weight gain, hospitalization duration, or blood antioxidant levels. The improvement seen in both groups was attributable to standard medical care, not the supplement.
Researchers tested whether hazelnut skin extract could help young dairy calves recover from diarrhea, a serious illness that affects many calves on farms. Sixty calves were split into two groups: one received the hazelnut extract along with standard treatment, while the other received only standard treatment. After five days, both groups improved equally well, suggesting that the hazelnut extract didn’t provide extra benefits beyond what regular medical care already provides. This finding matters because farmers are looking for natural alternatives to antibiotics, but this particular extract didn’t prove helpful for this purpose.
Key Statistics
A 2026 randomized controlled trial of 60 hospitalized dairy calves found that oral hazelnut skin extract supplementation provided no additional clinical benefits compared to standard treatment alone for neonatal diarrhea.
In a five-day study of 60 calves with diarrhea, both the hazelnut extract group and control group showed identical recovery rates, with no significant differences in fecal scores, hydration status, milk intake, weight gain, or hospitalization duration.
Blood oxidative stress markers showed no significant differences between calves receiving hazelnut extract and control calves in a 2026 clinical trial, despite hazelnut skin containing polyphenol compounds with theoretical antioxidant properties.
The Quick Take
- What they studied: Whether giving young calves hazelnut skin extract would help them recover faster from diarrhea when combined with standard medical treatment
- Who participated: Sixty female Holstein dairy calves (a common breed) that were hospitalized with neonatal diarrhea, divided equally into two groups of 30 calves each
- Key finding: Both groups of calves improved at the same rate over five days. The calves receiving hazelnut extract showed no better recovery, weight gain, or blood antioxidant levels than calves receiving only standard treatment
- What it means for you: While hazelnut extract is a natural product with potential health benefits, this study found it didn’t help sick calves recover from diarrhea. Farmers should continue relying on proven medical treatments rather than expecting natural supplements to replace standard care. More research may be needed to determine if hazelnut extract could help in different situations or at different doses
The Research Details
This was a randomized controlled trial, which is one of the strongest types of scientific studies. Researchers randomly divided 60 sick calves into two equal groups to ensure fair comparison. One group received 10 grams of hazelnut skin extract mixed with their milk for five days, while the other group received only their regular milk and standard medical care. All calves in both groups received the same basic treatments: fluids to prevent dehydration, antibiotics when needed, and standard farm care.
The researchers carefully tracked many measurements throughout the study. They recorded how quickly each calf’s diarrhea improved, how much milk each calf drank, weight changes, how long calves stayed hospitalized, and blood tests to measure oxidative stress (a type of cellular damage). By measuring so many different outcomes, the researchers could see if the hazelnut extract helped in any way.
This type of study design is important because randomly assigning calves to groups helps prevent bias. If researchers had let farmers choose which calves got the extract, the results might have been skewed. Random assignment makes it much more likely that any differences between groups are due to the treatment itself, not other factors.
This research approach matters because it directly tests whether a natural product works in real-world conditions. Rather than just testing hazelnut extract in a laboratory, researchers used actual sick calves receiving actual medical care. This makes the findings more relevant to farmers and veterinarians. The study also matters because it addresses a real problem: antibiotic resistance. Bacteria are becoming resistant to antibiotics, making infections harder to treat. Scientists are searching for natural alternatives, and hazelnut extract seemed promising because it contains polyphenols, compounds with potential health benefits. However, this study shows that not every natural product works as hoped, even when it has beneficial compounds.
This study has several strengths that make its findings reliable. It was randomized, meaning calves were assigned to groups by chance rather than by choice, which reduces bias. The sample size of 60 calves is reasonable for this type of animal research. All calves received standardized care, meaning they were treated the same way except for the hazelnut extract. The researchers measured multiple outcomes rather than just one, giving a complete picture of whether the extract helped. However, the study lasted only five days, which is relatively short. It’s possible the extract might show benefits over a longer time period. Additionally, this study was conducted in hospitalized calves receiving intensive medical care, so results might differ in calves with milder illness or in farm settings without hospitalization
What the Results Show
The main finding was clear: hazelnut skin extract did not improve recovery from diarrhea in sick calves. Both groups of calves improved at nearly identical rates. Calves receiving the extract and calves receiving only standard treatment showed the same improvement in diarrhea symptoms, the same hydration status (how much water their bodies retained), and the same weight gain over the five-day study period.
Hospitalization duration was also the same for both groups, meaning calves didn’t go home any faster if they received the extract. Mortality rates were similar between groups, indicating the extract didn’t reduce the risk of death. Blood tests measuring oxidative stress markers showed no significant differences between the two groups. Oxidative stress is cellular damage that can slow healing, so researchers expected the extract might reduce this damage since hazelnut skin contains antioxidants. However, no such benefit appeared.
The good news was that both groups improved substantially. This improvement was clearly due to the standard medical treatments all calves received, including fluids, antibiotics, and supportive care. The fact that both groups recovered well shows that current standard treatments are effective for most calves with diarrhea.
Milk intake was similar between groups, suggesting the extract didn’t improve appetite or digestive function. Sepsis scores, which measure how sick a calf is from infection, improved equally in both groups. This indicates the extract didn’t help fight infection or reduce the severity of illness. The researchers also looked at whether the extract caused any harmful side effects. No adverse effects were reported in either group, so the hazelnut extract appeared safe to give to sick calves, even if it wasn’t beneficial.
This study fits into a larger picture of research on natural compounds for animal health. Previous laboratory studies have shown that hazelnut skin contains polyphenols with antioxidant and anti-inflammatory properties. However, this clinical trial demonstrates that having beneficial compounds in a product doesn’t guarantee it will help sick animals. The gap between laboratory results and real-world outcomes is common in medical research. Other natural supplements have shown similar patterns: they work in test tubes but don’t translate to clinical benefits in living animals. This study adds to growing evidence that natural doesn’t automatically mean effective, and that rigorous testing is necessary before recommending any supplement for medical use.
Several limitations affect how we interpret these results. First, the study lasted only five days, which is relatively short. It’s possible the extract might show benefits if given for longer periods. Second, all calves were hospitalized and receiving intensive medical care, so results might differ in calves with milder illness or in farm settings. Third, the dose of 10 grams per day was chosen somewhat arbitrarily, and different doses might produce different results. Fourth, the study only included female Holstein calves, so results might not apply to other breeds or to male calves. Finally, the study didn’t measure whether the extract affected the calves’ gut bacteria, which play an important role in digestion and immunity. Future research might explore these areas
The Bottom Line
Based on this research, hazelnut skin extract should not be used as a substitute for standard medical treatment in calves with diarrhea. Continue using proven treatments including fluid therapy, appropriate antibiotics, and supportive care. If farmers are interested in natural supplements, they should wait for more research before investing in hazelnut extract for this purpose. The confidence level for this recommendation is moderate to high, based on a well-designed randomized trial, though additional studies would strengthen the evidence.
Dairy farmers, veterinarians, and animal health professionals should pay attention to this finding. Anyone considering hazelnut extract as a treatment for calf diarrhea should know it didn’t help in this study. However, this finding doesn’t mean hazelnut extract has no value for other purposes or other animals. Researchers interested in natural alternatives to antibiotics should consider this a learning point: natural compounds require rigorous testing before clinical use. People interested in sustainable agriculture should note that while hazelnut skin is a good source of polyphenols and a sustainable by-product, its benefits may be limited to certain applications.
In this study, calves were monitored for five days, and both groups showed improvement within this timeframe. If hazelnut extract were to help, benefits would likely appear within the first week of treatment. Farmers should not expect delayed benefits from this supplement. Recovery from calf diarrhea typically takes 3 to 7 days with standard treatment, and this study found the extract didn’t speed up this natural recovery process
Frequently Asked Questions
Does hazelnut extract help calves recover from diarrhea?
A 2026 clinical trial of 60 calves found hazelnut extract provided no additional benefit beyond standard medical treatment. Both treated and untreated calves recovered at identical rates, suggesting standard care alone is sufficient for recovery
Can natural supplements replace antibiotics for treating sick calves?
This study found hazelnut extract, a natural supplement, did not improve outcomes compared to standard treatment. While natural products may have potential, they require rigorous testing before replacing proven medical therapies
Is hazelnut skin extract safe to give to sick calves?
The study reported no adverse effects from hazelnut extract in either group of calves, indicating it appears safe. However, safety doesn’t mean it’s effective, and this supplement showed no clinical benefits in this trial
What should farmers do to treat calf diarrhea?
Continue using standard proven treatments including fluid therapy for hydration, appropriate antibiotics when needed, and supportive care. This study confirms these conventional approaches work well and should remain the foundation of treatment
Why didn’t hazelnut extract work even though it contains antioxidants?
Laboratory compounds don’t always translate to clinical benefits in living animals. While hazelnut skin contains beneficial polyphenols, the five-day dose used in this study didn’t reduce oxidative stress or improve recovery compared to standard treatment alone
Want to Apply This Research?
- If a farm uses this supplement, track daily diarrhea severity scores (1 to 5 scale), milk intake volume in liters, and body weight in kilograms for each treated calf. Compare these metrics between treated and untreated calves over 7 days to determine if the supplement provides any observable benefit beyond standard care
- Rather than adding hazelnut extract to standard treatment, focus on optimizing proven interventions: ensure adequate electrolyte replacement, maintain proper milk feeding schedules, monitor hydration status daily, and follow veterinary guidance on antibiotic use. Use the app to track these core interventions and their outcomes
- Create a long-term tracking system that monitors calf diarrhea incidence rates, recovery times, and mortality rates on your farm. Compare these metrics before and after any new supplement introduction. This helps you identify whether new products actually improve outcomes or simply add cost without benefit. Track at least 20 to 30 cases per group for meaningful comparison
This research was conducted in hospitalized dairy calves receiving intensive medical care and may not apply to all situations or all animals. Hazelnut skin extract should not be used as a replacement for standard veterinary treatment of calf diarrhea. Always consult with a veterinarian before starting any supplement or changing treatment protocols. This article summarizes research findings and is not medical advice. Individual results may vary, and treatment decisions should be based on professional veterinary guidance specific to your animals and situation
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.