Animal Waste Used as Livestock Feed: Dangers to Human Health
Every year, up to seven million Americans fall victim to foodborne illness. While the blame usually goes to overworked slaughterhouse inspectors who allow traces of manure to remain on meat, or to careless cooks who have not sufficiently nuked the uninvited guests in meat, there is another contributor: many farmers routinely mix chicken excrement into cattle feed. In the September-October 1997 issue of Preventive Medicine, PCRM’s Eric Haapapuro, Neal D. Barnard, M.D., and Michele Simon, J.D., M.P.H., exposed this common, if little-known, practice.
Every year in the U.S., seven billion chickens are raised and slaughtered. Along with the hundreds of millions of cattle, pigs, and other animals raised to satisfy America’s appetite for meat, they produce more than 1.6 billion tons of waste each year. Disposing of this huge load of excrement has become a serious environmental problem for many farmers. Chicken litter, in particular, has been linked to pollution and the growth of dangerous organisms in sensitive waterways.
An official with the Extension Poultry Science Department of the University of Georgia described the problem as a massive one in his comments to the Food and Drug Administration: “The magnitude of the problem may be visualized by comparing the waste voided by man and the animals he raises. For example, a cow generates as much manure as 16.4 humans; one hog produces as much as 1.9 people; and seven chickens provide a disposal problem equivalent to that created by one person. As a result, farm animals in the United States produce 10 times as much waste as the human population.”
Farmers have turned to mixing animal wastes, particularly chicken litter, into livestock feed. In Arkansas, 18 percent of chicken farmers use their accumulated chicken litter for cattle feed. In 1994, they used 2.6 million pounds of chicken litter as livestock feed and sold 160 tons for use as feed. Federal law does not touch it, and state laws apply to commercial feed manufacturers, rather than to farmers who use excrement produced on their own or a neighbor’s farm.
Chicken wastes are a well-known source of salmonella and campylobacter. The usual “treatment” is to simply pile it up and let it sit, a process called “deep stacking.” When wastes are piled to a height of about five feet, spontaneous heating and dehydration occur, which farmers hope will inactivate bacteria. However, inactivation of some salmonella species requires temperatures of approximately 145°F. The temperatures in stacked poultry litter usually only reach 110°F to 140°F, and the higher the moisture content, the lower the temperatures achieved. Survival of even small numbers of bacteria can be dangerous. Some strains of Salmonella typhimurium are so highly infectious that ingestion of fewer than ten cells can cause disease.
Have It Your Way
Disease-causing bacteria are a routine part of animal products. A 1994 USDA survey found that 15 percent of beef carcasses were tainted with disease-causing bacteria. About 30 percent of chicken products carry live salmonella, and 60 to 80 percent of chickens carry campylobacter. Many strains of these pathogens are resistant to common antibiotics. The feeding of excrement from one animal to another increases the risk that disease-causing bacteria will spread.