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

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

Jan. 1, 2011 - Dec. 31, 2011

2011-150

$169,575.00

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

Donna Henderson, E. Rob Atwill, Ph.D.

Final Report

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 office 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 survival 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 ftfor 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 beforehand 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.

Technical Abstract

Concerns are raised with all animal production systems and their wastes where there is an increased potential for microbial pathogens to enter the aerosol environment. Thus, an understanding of relative risks can only be put into perspective with a clear knowledge of the actual levels of the various organisms at realistic distances from production systems. The present study aims to address the issue of transfer and survival of key organisms in the surrounding natural aerosol environment under normal grazing conditions to assess an overall pattern of transmission. . 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 survival in animal feces, soil, and aerosols, as well as the pathogen movements through wind, water or flies. While the California Leafy Green Products Handler Marketing Agreement (LGMA) has suggested distances in their guidelines, they recognize that additional quantitative scientific data would help with their recommendations. This research project will be directed by UC Davis, with collaboration from UC Cooperative Extension, Imperial County, and the California Wool Growers Association. This project has as its primary objective to identify 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 to investigate the distance over which viable pathogens can be transferred by aerosolized particles.