Feeding poultry wastes to cattle: Potential health threats and the problem of traceability

Background. Recognition of the role of livestock feeding practices in the development of prion diseases has prompted widespread changes in agricultural industry standards, accompanied by new animal feed laws in several countries. While most of these laws prohibit the feeding of poultry litter to cattle, this practice continues legally in the United States.

Methods. A literature review was conducted to assess the methods by which poultry wastes may be processed and stored before being fed to cattle, and to identify human and animal health hazards potentially associated with these practices. To estimate the prevalence of litter-feeding practices and to characterize their regulation and oversight, data requests were sent to feed control personnel in 50 states and to agriculture faculty at major universities.

Results. Spilled feed and feces in poultry litter may permit transmission of prion diseases. Metabolites of poultry drugs may cause acute toxicity and contribute to the development of antimicrobial resistance. Inorganic arsenic from litter may accumulate to hazardous levels in beef cattle tissues. Enteric pathogens may thrive in litter that is improperly processed. Survey responses indicate that processing and storage methods are not regulated or monitored, while the few published guidelines on processing are imprecise, inconsistent, and frequently in conflict with microbiological studies of pathogen elimination. Survey results also indicate generally poor awareness of the prevalence of litter-feeding and suggest that most litter used in feed is traded or sold informally, potentially confounding food-safety traceback efforts.