Concerns about concentration of swine production into ''concentrated feeding operations'' and possibilities of odor nuisances and extensive emissions of ammonia, plus discharge of pathogens and contamination of surface and ground water with waste nutrients (especially nitrogen, phosphorus, copper, and zinc), have led to significant efforts to find economically and operationally viable alternatives to current waste management methods. While traditional swine waste management involved land application of material to meet nutrient needs of crop and/or animal feed production on the same location as where the animals were raised, the move toward separation of animal production from feed production locations has changed those practices. Waste management plans are now required for virtually any concentrated swine production facility that is economically viable in size. These plans have, until recently, been built around the requirement for available nitrogen by the crop to be fertilized by the waste. In 2003, the Environmental Protection Agency revised the Clean Water Act and included provision for regulation of waste application based on phosphorus as well as nitrogen. That process is under development at present, but it is certain that both nitrogen and phosphorus will be used in determining the amount of all animal waste that can be land-applied. The fact that many land areas that have received animal waste in the past based on nitrogen requirements have excessive levels of phosphorus poses a serious problem. Many animal operations cannot comply with the combined nitrogen and phosphorus requirements with existing land area and current animal numbers. The use of enzymes (especially phytase) in swine diets is becoming common, and this reduces phosphorus excretion by 40% or more. This practice will greatly improve, over time, the current imbalance in soil phosphorus found on many land application sites, but the remediation time will be extensive.
Increased awareness of the role of animal production in atmospheric emission of ammonia is resulting in concern not only in land application of measured waste nitrogen, but also the undesirability of loss of nitrogen as ammonia to the atmosphere with deposition elsewhere. Ammonia emission regulations are common in many countries already.
Odor emission, a local issue in animal production, is the greatest concern associated with the location of swine production facilities, and one that raises significant emotional concerns and legal challenges. For that reason, swine production systems must address and significantly reduce or eliminate odor concerns beyond their property boundaries.
Modern swine production practices involve use of elevated levels of both zinc and copper in the diets for immunity enhancement in young pigs (zinc) and growth promotion (copper). The positive aspects of these additions result in significant reduction in need for antibiotic use. The negative aspect is that these metals are excreted in the waste, which, when the waste is applied to land, can result in soil accumulations that interfere with growth of some plants.
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