Summary of Awards to Date

Developing buffer zone distances between sheep grazing operations and vegetable crops to maximize food safety.


Jan. 1, 2011 - Dec. 31, 2011

Award Number


Funding Agency

Center for Produce Safety

Amount Awarded



Bruce R. Hoar, Ph.D.
University of California, Davis


D. Henderson, R. Atwill


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
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.