In 1992, the United States had about 450,000 facilities that confined livestock or poultry 3 . State water quality surveys identify agriculture as the leading cause of impairment of rivers, streams, and lakes not meeting water quality goals. About a quarter of the river and stream miles impaired by agriculture have pollution from feedlots 4 . Most of the pollution from farm animals is due to manure. However, improper disposal of dead animals also poses a pollution risk.
Animal waste contains several potential water pollutants.
It releases basic plant nutrients like phosphorus and nitrogen. Too much of these in surface waters can lead to algal blooms, oxygen depletion, and fish kills. Researchers have linked high nutrient levels with outbreaks of dangerous microbes, like Pfiesteria. Manure may also directly contribute fecal coliform bacteria and pathogens like Cryptosporidium. Some manure also contains traces of hormones, heavy metals, or antibiotics.