Could Chicken Manure Be the Cause of Bird Flu Outbreaks in Cattle? Here’s What You Need to Understand.

Bird flu outbreaks have impacted 34 dairy cow herds across nine states, sparking speculation about whether the use of contaminated poultry litter as cattle feed could be the transmission source, although experts caution that insufficient data is available to make this determination.

KEY FACTS Poultry litter, a blend of chicken feces, feathers, and bedding materials such as sawdust, peanut hulls, and pine shavings collected from chicken coops, is commonly utilized as both fertilizer and cattle feed, as outlined in a study published in the International Journal of Environmental Research and Public Health.

While federal regulations are lacking, certain states like California prohibit the use of poultry litter as feed for lactating dairy cows—the sole cows affected by the circulating bird flu outbreaks in the U.S.—while still permitting its use in beef cows and other cattle.

Studies indicate that chicken litter may contain bacteria such as salmonella and E. coli, prompting concerns among some experts that the feed consumed by cows could harbor traces of the bird flu virus, potentially leading to outbreaks in cattle.

Nonetheless, there is insufficient information regarding how cows contracted the virus from birds to establish a definitive link, as noted by Jodie Guest, senior vice chair of the Department of Epidemiology at Emory University’s Rollins School of Public Health, who told Forbes, “We also do not have a good understanding of how common this practice is.” Without knowledge of how many affected herds utilize chicken litter as feed, “it would be really hard to link these two together.”

The Department of Agriculture attributes the outbreaks to wild migratory birds, although it has confirmed that infected unpasteurized milk may contribute to cow-to-cow transmission.

Forbes has sought comment from the Food and Drug Administration.

KEY BACKGROUND Poultry litter serves as cattle feed due to its cost-effectiveness as a protein source and its utility in waste disposal, according to the Department of Animal Sciences at the University of Missouri. While the FDA initially discouraged its use in 1967, it reversed this recommendation in 1980, allowing individual states to decide.

 Following the detection of the first case of bovine spongiform encephalopathy (mad cow disease) in the U.S., the FDA implemented a temporary ban on feeding poultry litter to cattle in 2003 to prevent disease spread. However, this ban was later rescinded, with a prohibition on cow brains and spinal fluid—known to transmit mad cow disease—in chicken feed instead. This decision was made because chickens could potentially transmit mad cow disease to cows via poultry litter if they consumed infected cow brains and spinal fluid. The European Union and Canada have banned the use of chicken litter as animal feed due to disease transmission risks, such as those associated with mad cow disease.

TANGENT This incident echoes previous instances of bird flu transmission to animals via contaminated food. In 2023, around 30 cases of bird flu were reported in domestic cats, with concerns raised about contaminated mink meat making its way into cat food amid a potential mink outbreak, according to The New York Times. The European Union’s largest mink farm operator, Poland, experienced a previous bird flu outbreak on mink farms in Spain, marking the first evidence of mammal-to-mammal virus transmission. In 2023, bird flu was also detected in cat shelters in South Korea, prompting officials to recall specific cat food types due to suspected food-related transmission.