Poultry Litter: A Potential Source of Avian Flu in Cattle
As epidemiologists scramble to determine how dairy cows across the Midwest became infected with a strain of highly pathogenic avian flu, they are examining a common practice employed by farmers: the feeding of animal waste and parts to livestock raised for human consumption.
It is still unclear how the cows were infected – whether by contact with birds or via feed made from litter waste – but litter has been associated with previous outbreaks of disease, including botulism. Poultry litter consists of manure, feathers, spilled feed, and bedding material that accumulates on the floors of buildings housing chickens and turkeys. It can contain disease-causing bacteria, viruses (including H5N1), antibiotics, toxic heavy metals, pesticides, and even foreign objects such as dead rodents, birds, rocks, nails, and glass.
Most other developed nations, including Canada, the United Kingdom, and the countries within the European Union, have banned the practice of feeding poultry litter to cattle. The FDA considered doing so in the U.S. in the mid-2000s. However, for cattle farmers, the waste provides a cheap form of protein feed, while for poultry farmers, it allows them to divert the litter away from landfills or burning.
While the FDA mandates the removal of all tissues shown to carry prions – such as brains and spinal cords – from poultry diets to reduce the risk of mad cow disease, other more common pathogens are also found in poultry litter. In one 2019 study of litter used on farm fields as fertilizer, researchers found that every sample tested from U.S. broiler chickens carried E. coli strains resistant to more than seven antibiotics.
California has banned the feeding of poultry litter to lactating dairy cows, but it is still legal to sell it as feed for beef and other cattle. The state requires that animal waste products sold for feed must contain no residues of pathogens, metals, pesticides, or antibiotics. However, it is unclear whether there are regulations addressing the private exchange or production of poultry litter or other animal waste for feed or how widespread the practice is in the state or around the country.
The federal government does not regulate poultry litter in animal feed, and in many states, there are no requirements or regulations regarding contamination or processing. The FDA may take regulatory action if it becomes aware of food safety concerns with poultry litter products intended for use in animal food in interstate commerce.
