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Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2001
Publication Date: 7/1/2002
Citation: Varel, V.H. 2002. Livestock manure odor abatement with plant-derived oils and nitrogen conservation with urease inhibitors. Journal of Animal Science. 80(E.Suppl. 2):E1-E7.

Interpretive Summary: Livestock production has changed over the last few decades and is now challenged with environmental and food safety issues. Nutrient management, odor emissions and pathogenic microorganisms associated with livestock must be resolved with safe and cost effective treatments. This requires a multidisciplinary approach and one solution is not universal to all production facilities. Microorganisms play a central role in many of the production issues, therefore, microbial activities should be addressed. Chemical additives which affect key metabolic pathways (urea hydrolysis), or additives which serve as antimicrobial agents (plant-derived oils) may offer multiple solutions for sustainable livestock production. Additives must be thoroughly evaluated and tested before one can expect producers to use them on a broad basis.

Technical Abstract: Confined animal feeding operations are under environmental scrutiny for production of large quantities of waste in a small area. The waste can result in odor, global warming gases and the transfer of nutrients and pathogens to water and food sources. Our objectives are to provide simple, cost effective, and environmentally sound solutions to control odor and pathogens in livestock waste, with nutrient management a top priority. A urease inhibitor, N-(n-butyl) thiophosphoric triamide, was used to reduce urea hydrolysis in beef cattle feedlot pens, conserve nitrogen, and inhibit ammonia emissions which contribute to odor. Laboratory studies with antimicrobial plant-derived oils, thymol and carvacrol, at 2 g kg**-1 of feedlot waste completely inhibited the production of VFA in flasks over 23 days. Fecal coliforms were reduced from 4.6 x 10**6 to 2.0 x 10**3 cells ml**-1 2 days after treatment, and were nondetectable within 4 days. These central plant oils are not degraded under anaerobic conditions. However, our feedlot studies and the literature indicate these oils are degraded under aerobic conditions. This suggests that these generally recognized as safe (GRAS) chemicals, which are routinely used as preservatives in food and personal care products, should not accumulate in soils to which this waste is applied. It is concluded, that chemical additives can be added to animal waste to prevent degradation, which in turn controls odor emissions, reduces pathogens, and conserves nutrients until the waste can be recycled as fertilizer. The economics and environmental effects of using thymol and carvacrol in livestock production facilities need to be determined.