Cornell Study Finds Grape Waste May Replace Chicken Antibiotics

Researchers at Cornell say a waste product from wine and juice production could help chicken farms reduce their reliance on antibiotics, offering a possible new use for grape pomace, the pulpy mix of skins, seeds, stems and peels left after grapes are pressed.

In a study published May 7 in npj Biofilms and Microbiomes, food scientists tested whether grape pomace could replace zinc bacitracin, a widely used antibiotic growth promoter in broiler feed. The team found that adding just 0.5% grape pomace to the diet of young chickens raised on an inflammation-inducing feed improved weight gain, feed efficiency and gut health in ways that came close to the antibiotic group.

The work comes as poultry producers face growing pressure to cut back on antibiotics because of concerns about antimicrobial resistance. Antibiotic growth promoters have already been banned in the European Union, China and Brazil, but not in the United States. Researchers said the need for alternatives remains urgent because farmers still want birds that grow efficiently without chronic gut inflammation slowing them down.

Elad Tako, an associate professor of food science at Cornell and the study’s corresponding author, said the results suggest that a small amount of grape pomace can make a meaningful difference. He said the team had been studying the material as a functional ingredient for both people and animals and called the findings a turning point.

To mimic stress conditions common in commercial poultry operations, including poor-quality feed ingredients and crowded housing, the researchers fed 126 broiler chickens a diet containing 30% rice bran, a high-fiber ingredient known to trigger low-grade intestinal inflammation. Birds on that diet alone gained less weight and showed higher levels of inflammatory markers. When grape pomace was added, weight gain improved by at least 79% compared with birds on the inflamed diet without the supplement, and feed conversion improved to levels similar to those seen in birds given zinc bacitracin.

The study also examined fermented versions of the pomace made with Lactobacillus casei and Saccharomyces cerevisiae. Fermentation slightly lowered total polyphenols, the plant compounds believed to drive some of the anti-inflammatory effects, but both fermented forms performed at least as well as raw pomace on most measures. The version fermented with bacteria produced a larger villus surface area in the small intestine, which can improve nutrient absorption.

The researchers said the supplement also changed the birds’ gut microbiome in ways that appeared beneficial. Levels of Klebsiella and Clostridium, bacteria linked to intestinal disease, fell to levels similar to those in the antibiotic group. Butyrate production increased as well. Butyrate is a short-chain fatty acid that helps feed cells lining the gut and plays a role in controlling inflammation.

The appeal of grape pomace is not only biological but practical. The material is produced in large quantities every year by wineries and juice makers, much of it ending up in landfills or compost streams. Turning even part of that waste into a feed additive could give wineries another outlet for a byproduct they often struggle to dispose of while also helping poultry producers reduce antibiotic use.

Tako said more testing is needed before the approach can be used widely, especially under commercial farm conditions with far larger flocks. He said his current contacts are mostly on the wine and pomace-production side rather than with poultry companies.

Cornell co-authors included Milan Sharma, Nikita Agarwal, Sara Stadulis, Eliot Dugan, Chloe Giovannoni, Peter Gracey, Melissa Huang and Patrick Gibney. Additional researchers were from Arizona State University’s Biodesign Institute.