Close to one-third of the earth’s entire land surface is used to raise farmed animals such as cattle. In the United States, 92.6 million heads of cattle were recorded as of January 1, 2011. Both intensive and non-intensive livestock operations have been known to impact the quality of surrounding water bodies. Intensive operations include feedlots, which have more than 500 heads of cattle, while non-intensive operations include pasture, cow-calf operations and watering sites for cattle. A number of high-profile cases of drinking water wells tainted by cow manure have been reported to cause the hospitalization and death of hundreds of people around the world. A high dose of animal waste in surface waters can also cause algal blooms that kill fish and other marine life. Cattle fecal contamination can contribute to both point and non-point sources of water pollution.
Point Sources of Cattle Fecal Pollution
Waste products from cattle are discharged from a single, identifiable source.
Manure Mismanagement in Concentrated Animal Feeding Operations
Large farms raising cows are known as concentrated animal feeding operations (CAFOs). Cattle are kept and raised in confined areas. Feed is brought to the animals and their wastes are collected in storage structures. The National Pollutant Discharge Elimination System under the Clean Water Act requires CAFOs to get a permit from the state and the U.S. Environmental Protection Agency before they can discharge their waste into any body of water. CAFOs are required to treat their effluents and reduce the level of pollutants. But if farm operators do not treat cattle waste, then harmful pathogens found in cow feces can enter nearby water bodies as raw sewage. These pathogens include Bacteroidetes
that are found in large quantities in the feces of warm-blooded animals. Certain strains of the Bacteroides
genus have been found in cattle. As such, these bacterial strains can be used as indicators of cattle fecal contamination when conducting microbial source tracking analysis. Source Molecular's Cow Bacteroidetes ID
™ service uses quantitative polymerase chain reaction (qPCR) DNA technology to determine the presence of cattle fecal contamination. qPCR allows quantities of DNA to be amplified into a large number of small copies of DNA sequences. This is accomplished with small pieces of synthetic DNA called primers that are complementary and specific to the Bacteroidetes
Agricultural Anaerobic Lagoon or Manure Lagoon Spills
Beef and dairy CAFOs manage and treat cattle waste through a system that includes anaerobic respiration. Cattle feces are washed out from underneath animal pens. This manure slurry is then piped into an anaerobic lagoon or manure lagoon, which is a man-made outdoor earthen basin, or sometimes it can be placed in an intermediary holding tank under or next to the barns before it is deposited in the lagoon. The slurry, once settled in the lagoon, separates into solid and liquid layers. The manure then undergoes the process of anaerobic respiration, whereby the volatile organic compounds are converted into carbon dioxide and methane. Depending on the size of the CAFO, the lagoons could be the size of several football fields. Lagoon overflow is a pressing environmental concern. It happens when there are cracks or when the lagoon is improperly constructed or when there's a heavy downpour. The devastating effects of manure lagoon spills led to stricter regulation of the CAFO by the EPA with some states following suit. North Carolina even banned the construction of new anaerobic lagoons in 1999 after two major spills resulted in the death of millions of fish and closure of coastal wetlands to shellfishing.
Some farms allow their range cattle to have direct access to streams, lakes, reservoirs or dugouts, which creates problems with water quality because cows not only drink the water but also defecate in and around it. This not only affects the cow's health and productivity but also agricultural and non-agricultural downstream users. Many pathogens that reside in cattle are infectious to humans. This underscores the importance of better waste management practices in farms.
Non-Point Source of Cattle Fecal Pollution
Fecal matter from cattle winds up in water bodies in a diffuse manner. Agricultural non-point source pollution was the leading source of water quality impacts on surveyed rivers and lakes in the year 2000.
Agricultural or Farm Run-off
Agricultural or farm runoff is considered as one of today’s biggest environmental threats. Runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater or other sources flows over the land and falls into ditches, creeks, rivers and lakes. In agricultural or farm lands, cattle manure is most often used as fertilizer and is usually spread on fields. Thus, the runoff would include cattle fecal matter as well as other synthetic fertilizers and chemicals present in the land. A study had found that runoff is proportionately higher from a heavily grazed watershed than moderately or lightly grazed watersheds because the soil would be compacted by cattle hooves. Another study found that during winter, surface runoff increases because the ground would be frozen making it difficult for cattle manure to be absorbed into the soil.
An article published in Animal Frontiers magazine in April 2012 noted that too often illnesses triggered by food and water intake, especially in rural areas, are assumed to be caused by livestock manure contamination. But most of the time, MST analysis would reveal that the pathogen causing the illness is associated with human feces rather than animal waste. Source Molecular therefore recommends using more than one test and testing for two or more hosts (such as cattle and human) simultaneously in order to achieve greater sensitivity and reliability with the results, which would facilitate in crafting best management practices.