Animal Manure May Contain Disease-Causing Bacteria, Viruses
That Can Reduce Water Quality
Dairy Pipeline: May 2000
Gerald M. (Jerry) Jones
Extension Dairy Scientist, Milk Quality and Milking Management
Animal manure may contain pathogenic (disease-causing) microorganisms (bacteria, viruses) that can reduce water quality. Transmissible livestock diseases from pathogens do threaten humans. Examples include Salmonella, E. coli, Johne's, leptospirosis, listeriosis, TB, tetanus, anthrax, cryptospirosis, etc. The soil-climate environment is hostile to such microorganisms. Over 90% of bacteria can be removed by filtration in the soil, but different soils have different filtering ability. Also bacteria can be transported by water moving through soil. Microorganisms seldom seep to groundwater from land-applied manure, properly functioning lagoons, or earthen manure storages. However, they remain a threat where they can pass through a shallow layer of coarse sand to fractured rock. Dairy waste, whether fresh, dry, or in liquid storage, may contain high concentrations of coliform bacteria (E. coli, enterococci) which are potentially hazardous to cattle and human health. Fecal coliforms are a problem to human drinking water if the bacteria are in high concentration. Manure is a potential contaminant of domestic wells. Fecal bacteria can infiltrate wells when the manure management system and domestic well are not properly maintained. It is not known if the elevated coliform counts originated from human, livestock or wildlife (deer, ducks, etc.) sources. The first barrier to safeguard drinking water is to implement a herd health program that focuses on keeping cows and youngstock healthy. In addition to preventing disease, this includes isolating and treating infected animals. The second barrier is to reduce the likelihood that pathogens leave the farm. Collect all manure-contaminated runoff in a holding pond or in the manure-storage facility. Keep manure on concrete areas and control the runoff flow by constructing curbs. Land apply waste on sunny, warm days according to an approved nutrient management plan. Apply waste to crops that are growing and that will not be eaten or grazed until there is adequate time for bacteria and viruses to die-off. Limit the amount of manure applied to a single site to reduce the possibility of pathogenic bacteria buildup. And apply animal manure when the soil is not saturated and when rain is not forecast. A third barrier is to keep pathogens from polluting a watershed, such as spreading manure on a hillside or excess slope or encouraging livestock to avoid entering streams. This also means that streams should not flow through calf pastures or loafing lots or barnyards.