ITHACA, N.Y. – Every year, millions of gallons of wine are pressed, leaving behind a mountain of pulpy residue – grape skins, seeds, stems and peels – that wineries struggle to dispose of. Now, Cornell University researchers say this overlooked byproduct could serve as a replacement for the antibiotics routinely added to chicken feed.
A team of food scientists tested grape pomace as an additive in broiler chicken diets, comparing it head-to-head against zinc bacitracin, one of the most widely used antibiotic growth promoters in the poultry industry. The paper published in npj Biofilms and Microbiomes .
The results are striking, said corresponding author Elad Tako , associate professor of food science, suggesting that a modest half-percent inclusion of grape pomace in feed can nearly match the antibiotic's performance – improving weight gain, feed efficiency and gut health in birds raised on an inflammation-inducing diet.
"We've been studying this as a functional food ingredient for both humans and animals, and this is a defining moment," Tako said. "We were able to mitigate low-grade inflammation, which is status quo in the poultry industry."
The withdrawal of antibiotic growth promoters from broiler production, driven by mounting concern over antimicrobial resistance, has long been associated with slower-growing, sicker birds and higher feed costs. The poultry industry has scrambled for alternatives, but few have matched antibiotics' dual punch: suppressing harmful bacteria while simultaneously reducing the low-grade gut inflammation that quietly saps a bird's growth energy.
"There is a full ban of the use of antibiotic growth promoters in the EU, China and Brazil," Tako said. "There's not yet a formal ban in the U.S., but there's a significant need because of the threat of introducing antibiotic resistance."
To simulate the kind of intestinal stress that commonly affects commercial flocks, researchers fed 126 young broilers a diet containing 30% rice bran, a high-fiber ingredient known to trigger chronic low-grade inflammation in the gut. Birds on this diet alone showed significantly reduced weight gain and elevated levels of two proteins that serve as molecular signals of inflammation.
When grape pomace was added at just 0.5% of the diet, body weight gain improved by at least 79% compared to inflamed birds given no supplement, and feed conversion (a key measure of how efficiently birds turn feed into body mass) improved to levels on par with the antibiotic group. The improvements held through the final days of the 42-day experiment.
"Previous research by others showed negative effects of pomace in the feed because it was too much of a good thing," Tako said. "What we did was revisit the approach and reduce the dose."
Redirecting even a fraction of grape pomace, a waste product, into poultry feed additives could create a circular economy benefit while addressing one of agriculture's more pressing drug resistance problems.
If widely adopted, this small change could serve as an effective alternative to antibiotic growth promoters in broiler production, dramatically reducing costs for chicken farmers.
