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Developing Buffer Zone Distances Between Sheep Grazing Operations and Vegetable Crops to Maximize Food Safety

Atwill, Edward; Hoar, Bruce
University of California - Davis
Start date
End date
Integrated livestock and crop operations are beneficial to producers of both products. Crop residues are an important source of food for livestock, however domestic and wild animals represent a potential source of food borne pathogens.

Recent outbreaks of human infection with E. coli O157:H7 and other bacteria linked to consumption of California produce have raised concerns that sheep and other ruminants may elevate levels of pathogens within the soil, which have the potential of being transmitted to produce fields via aerosols.

The California Leafy Green Products Handler Marketing Agreement (LGMA) of January 2010 lists sheep as one of five mammalian species as "Animals of Significant Risk" and any intrusion by such animals requires a detailed food safety assessment prior to harvest. "Buffer zones" between the crop production fields and livestock operations are important in order to prevent the potential transmission of pathogens from animals to crops.

Currently, there is a paucity of information related to appropriate combinations of time and distance between livestock operations and crop systems, particularly in terms of pathogen survivai in animal feces, soil, and aerosols, as well as the pathogen movements through wind, water or flies. The LGMA suggests that a distance of 400 ft exist between a concentrated animal feeding operation and the edge of a crop and 30 ft for grazing lands/domestic animals, but recognize a lack of science on which to base this recommendation.

This proposed research aims 1) to investigate factors associated with the survival of bacterial pathogens from initial deposition as feces, to presence in soil before and after irrigation events, to presence of pathogens in dust generated in fields with active livestock grazing, and 2) to investigate the distance over which pathogens can be transferred by aerosolized particles.

Funding Source
Center for Produce Safety
Project number
Bacterial Pathogens
Meat, Poultry, Game