Effects of Dietary Manipulation on Pig Performance, Manure Composition, Hydrogen Sulfide and Ammonia Levels in Swine Buildings
Purdue University 2000 Swine Research Report. Excess excreted nutrients and emissions from swine production facilities continue to draw public attention as the rural-urban interface narrows and the threat of environmental impact grows. N-containing compounds originating from intensive agriculture are contributing to a decline in forest health and species diversity in the Netherlands (van der Eerden et al., 1998) and increased nitrate concentrations in groundwater in Canada (Zebarth et al., 1998). In swine buildings, low levels of NH3 (25 ppm) induced nasal irritation and depression of growth in pigs (Urbain et al., 1994), while Zhang et al. (1998) reported that air quality in a confinement swine building can cause acute respiratory responses in humans. Additionally, phosphorus accumulation in the soil could pose a threat to both groundwater and surface water quality. Manipulation of swine diets has been shown to be effective at decreasing N excretion of pigs by feeding diets that contain reduced levels of crude protein (CP) supplemented with essential synthetic amino acids (Gatel and Grosjean, 1992). Urinary N is reduced dramatically while fecal N remains relatively constant (Kerr and Easter, 1995), which limits NH3 emission (Canh, 1998). Feeding fermentable carbohydrates such as soybean hulls has been used to effectively reduce the ammonia emission from manure. The use of the phytase enzyme has been shown effective in liberating approximately 30% of the previously unavailable P from its phytic acid form in cereal grains. Spencer et al. (2000) reported that low-phytate corn (Lpa-1) contains at least 5 times as much available P as normal corn with a bioavailability near 62%. Recent research has indicated that there is a tendency for lower hydrogen sulfide levels in buildings where pigs are fed diets with lower sulfur content.