Gram Research analysis of a 2026 study found that adding defatted olive seed flour to chicken feed at 2 to 3 grams per kilogram produced generally favorable results. In 840 broiler chicks over 28 days, the supplement increased weight gain and improved feed efficiency, while no single level improved every outcome.
Gram Research analysis of a 2026 study in Frontiers in Veterinary Science looked at whether a leftover product from olive processing could help chickens grow well without antibiotic growth promoters. Researchers mixed defatted olive seed flour, a powder made from olive seeds after most of their oil is removed, into chicken feed at four different amounts. They followed 840 male broiler chicks for 28 days. Chickens eating 1 to 4 grams of the powder per kilogram of feed gained more weight and used their feed more efficiently than chickens on a plain diet. The gut bacteria also shifted toward more helpful types, and harmful germs such as Salmonella and E. coli decreased. Results looked generally best at 2 to 3 grams per kilogram, though no single amount improved every measure. This study was done in chickens, so it does not show direct effects on people.
Key Statistics
A 2026 randomized controlled trial of 840 male broiler chicks found that adding defatted olive seed flour to feed at every tested level increased final body weight and weight gain compared with a plain diet over 28 days.
In a 2026 study published in Frontiers in Veterinary Science, researchers used five diet groups with 12 pens per group and 14 chicks per pen, and found that results were generally most favorable at 2 to 3 grams of olive seed flour per kilogram of feed.
A 2026 study of broiler chickens reported higher levels of helpful Lactobacillus bacteria and lower levels of Clostridium, E. coli, and Salmonella in the ceca of birds fed olive seed flour over 28 days.
The Quick Take
- What they studied: Can adding a powder made from olive seeds to chicken feed improve growth, gut health, and immune signals in fast-growing chickens raised for meat?
- Who participated: 840 one-day-old male broiler chicks, a type of chicken raised for meat. The chicks were randomly split into five diet groups, with 12 pens per group and 14 birds per pen, and were followed for 28 days.
- Key finding: Chickens given olive seed powder at every tested level gained more weight and used their feed more efficiently than chickens on a plain diet. Results were generally most favorable at 2 to 3 grams per kilogram of feed, but no single level improved every outcome.
- What it means for you: This research applies to poultry farming, not to human diets. It suggests that olive seed powder may be a useful feed ingredient for chickens, but it does not show whether it is safe or helpful for people to eat.
The Research Details
Researchers set up a controlled experiment with 840 newly hatched male broiler chicks. The chicks were placed into five groups at random. One group ate a standard diet with no olive seed powder, and the other four groups ate the same standard diet with 1, 2, 3, or 4 grams of defatted olive seed flour added per kilogram of feed. Each group had 12 pens with 14 birds each, which helped reduce the chance that results came from chance alone.
Over 28 days, the team tracked how much the chickens weighed, how much weight they gained, and how efficiently they turned feed into body mass. At the end of the study, they examined blood chemistry, markers of oxidative stress (cell damage caused by unstable molecules), carcass traits, and the intestinal lining. They also measured the amounts of certain bacteria in the ceca, which are pouches in the chicken’s digestive tract, and checked the activity of genes linked to inflammation and immune response.
The design of this study is strong for animal nutrition research because the random assignment and the untreated control group allow the researchers to compare the powder’s effects directly. Using a fixed time period and a set number of birds also makes results easier to measure and repeat.
Random assignment means that differences between groups are more likely caused by the diet itself rather than by differences among the birds. Having a control group that ate the same feed without the powder makes it clearer which changes came from the olive seed flour. Testing several amounts also shows whether the effect changes with dose, which helps farmers and researchers think about practical feed levels.
The study appears well organized, with a large number of birds, multiple replicate pens, and a clear control group. It was published in a peer-reviewed veterinary journal. However, the findings come from a single 28-day trial in one type of chicken, and only male chicks were studied. The summary available for this analysis did not include exact percentages or p-values for each outcome, so readers should check the full paper for precise numbers before drawing detailed conclusions.
What the Results Show
The main result was that adding defatted olive seed flour to feed improved growth. Compared with the plain diet, every olive seed flour group showed higher final body weight, greater weight gain, and a higher production efficiency index, which is a combined score of growth, survival, and feed use. Feed conversion, meaning how much feed a bird needs to gain one unit of weight, also improved.
The gut results were encouraging as well. Chickens receiving the supplement had more Lactobacillus bacteria, a group often considered helpful for digestion. They also had fewer Clostridium, E. coli, and Salmonella bacteria, which include types linked to digestive illness. These shifts suggest the powder may support a healthier balance of microbes in the gut.
The study also examined inflammation and immune signals in the intestinal lining. The researchers measured how active certain genes were, including those for IL-10 and IFN-gamma, which are signaling molecules involved in controlling inflammation and immune response. The results suggest the supplement influenced these immune pathways, though the summary does not explain the direction of every change in detail.
Across all measures, the 2 to 3 grams per kilogram range produced the most generally favorable results. The authors note that no single inclusion level consistently improved every outcome, so the best amount may depend on which result a farmer or researcher cares about most.
The study also looked at blood biochemistry, markers of oxidative stress, carcass traits, and the structure of the small intestine lining under a microscope. The overall pattern suggests the olive seed powder may reduce some of the cell stress and inflammation that fast growth can cause. These secondary outcomes help explain why growth improved, since a healthier gut lining and lower inflammation can allow birds to absorb nutrients more effectively.
Olive products are known for polyphenols, plant compounds with antioxidant properties, and for fiber. Earlier research on olive-derived ingredients in animal feed has often reported similar benefits for antioxidant status and gut health. This study adds to that body of work by testing defatted olive seed flour, a byproduct that is less commonly studied than olive leaves or olive pomace, and by comparing several inclusion levels in one trial. Because the authors frame the powder as a possible alternative to antibiotic growth promoters, the results also fit a broader industry search for ways to raise healthy chickens without routine antibiotic use.
The study lasted only 28 days, so it does not show whether benefits continue through a full production cycle or whether they last after feeding stops. Only male broiler chicks were studied, so results may not apply to female birds, other chicken breeds, or other animals. The study also did not test olive seed flour in people, so it says nothing direct about human nutrition or safety. Finally, the summary available for this analysis did not include exact effect sizes for each result, which makes it harder to judge how large the differences were in practical terms.
The Bottom Line
Poultry producers and feed researchers may want to consider olive seed flour as a possible feed ingredient at 2 to 3 grams per kilogram, since this range gave generally favorable results in this trial (moderate confidence, based on one 28-day study). Further trials in different flocks, longer timeframes, and commercial farm settings would be needed before firm recommendations are made. People should not add this powder to their own diets based on this research.
Commercial poultry producers, animal nutritionists, and feed manufacturers may find this research relevant. Researchers studying alternatives to antibiotic growth promoters may also find it useful. General consumers, people looking for olive-based dietary supplements, and anyone seeking medical advice for themselves should not apply these findings directly, because the study was done only in chickens.
The study measured results over 28 days. Any benefits seen in that window cannot be assumed to continue for the full growing period of commercial birds or to carry over into different farm conditions. Farmers who try this approach would need their own trials to see how long-term growth, flock health, and costs compare with their current feeding program.
Frequently Asked Questions
Can olive seed flour be used as an alternative to antibiotics in chicken feed?
A 2026 study suggests it may help. Researchers tested defatted olive seed flour at 1 to 4 grams per kilogram in 840 broiler chicks over 28 days. The supplement improved growth and feed efficiency and shifted gut bacteria toward more helpful types compared with a plain control diet.
What amount of olive seed flour works best for broiler chickens?
In the 2026 study, 2 to 3 grams per kilogram of feed gave the most generally favorable results across growth, gut health, and immune markers. No single amount improved every outcome, so the best dose may depend on which goal matters most to the farmer.
Is olive seed flour safe for people to eat?
This study did not test olive seed flour in people, so it cannot show whether it is safe or useful in human diets. The research involved 840 broiler chicks fed the powder for 28 days. Anyone considering olive-derived supplements should talk with a doctor or registered dietitian first.
Why do fast-growing chickens need help with their gut health?
Fast-growing broiler chickens are prone to gut imbalance, oxidative stress, and inflammation, which can slow growth and affect health. In this study, olive seed flour, which contains fiber and plant compounds called polyphenols, was linked with more helpful gut bacteria and lower levels of harmful germs.
Want to Apply This Research?
- For users raising poultry, log body weight and feed intake weekly, then calculate feed conversion (kilograms of feed eaten divided by kilograms of weight gained) to compare against your baseline. For general users, track your interest in this topic by noting any new research you read, but do not log olive seed powder as a dietary change.
- If you keep a small flock, consider discussing olive seed flour with a poultry veterinarian or feed specialist before changing rations, and record any changes carefully. For personal diets, focus on whole foods you already know are beneficial, such as olive oil and high-fiber vegetables, rather than trying animal feed ingredients.
- Maintain a simple monthly log of key flock metrics such as average weight, feed conversion, mortality, and any signs of digestive upset, so changes can be compared over time. Review the full research and any new studies periodically, and treat single trials as one piece of evidence rather than a final answer.
This article summarizes an animal research study in broiler chickens and is for general information only. The findings do not apply directly to human diets, supplements, or health, and they should not be used to make medical decisions for people. Poultry producers should consult a veterinarian or qualified animal nutritionist before changing feed programs. Readers should consult a healthcare professional for personal health questions.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.