A cattle feedlot is a type of animal feeding operation used in intensive animal farming for finishing livestock, especially beef cattle. After some time naturally grazing, once cattle reach a certain weight they are placed inside a feedlot with the design of bulking them up to a required weight rapidly, so that they can be sent for slaughter. Here the cattle are fed a specialized animal feed which consists of corn.
Having so many cattle in close quarters means that there is a lot of excrement. And the feces of cattle carries pathogenic bacteria like Escherichia coli. To protect produce from contamination from pathogens, current regulations stipulate that there needs to be a buffer zone of 120 meters 400 feet from a feedlot.
New research suggests that this buffer zone, for the typical farm, is inadequate and that the distance needs to be increased in order to protect vegetables to be sold for human consumption.
For the study, microbiologists sampled leafy greens growing in nine plots. These were at 60, 120, and 180 meters downwind from the cattle feedlot (3 plots at each distance). The scientists found that the rate of contamination with the pathogenic E. coli declined (in this case, strain O157:H7 where infection may lead to hemorrhagic diarrhea, and to kidney failure). The rate of contamination decline varied with distance. This was from an average of 4 percent of samples per plot at 60 meters to 2 percent at 180 meters.
Different conditions affect the level of contamination. For instance, the researchers found that following a period of high cattle management activity when the feedlot was dry and dusty, including removal of cattle for shipping, the rate of total E. coli-contaminated samples per plot at 180 meters increased by over 90 percent.
Based on these findings, the researchers conclude that the high percentages of leafy greens contaminated with bacteria like E. coli mean that fresh produce should be planted at least 590 feet away from a feedlot. It is noted that the study was carried out in only one U.S. state (Nebraska) and actual distances will vary depending upon geography, weather, seasons and type of cattle rearing activities.
The research has been published in the journal Applied and Environmental Microbiology. The paper is headed “Effect of Proximity to a Cattle Feedlot on Escherichia coli O157:H7 Contamination of Leafy Greens and Evaluation of the Potential for Airborne Transmission.”
