Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2001
Publication Date: 10/1/2001
Citation: Miller, D.N. 2001. Accumulation and consumption of odorous compounds in feedlot soils under aerobic, fermentative, and anaerobic respiratory conditions. Journal of Animal Science. 79:2503-2512.
Interpretive Summary: Cattle feedlot odors are predominantly of microbial origin and are produced during the fermentative decomposition of animal wastes. This research suggests that the amount and persistence of malodorous VFA and aromatic compounds produced in anaerobic feedlot soils is dependent upon the amount and type of electron acceptor present. Application of this concept to feedlot production facilities--providing alternate electron acceptors, suc as nitrate or oxidized iron, wherever feedlot soils have become fermentative--may significantly reduce odor. Of course, larger scale tests at the feedlot pen level need to be conducted to determine the effectiveness of this proposed management strategy. Similarly, better control of anaerobic microbial processes may also benefit other types of confined animal production operations (i.e., swine) where odor is an issue.
Technical Abstract: This study examines the microbial potential for odor production and odor consumption in two soils from a cattle production facility in central Nebraska. The two soils tested were collected from a feedlot pen and a runoff ditch below the pen. These soils were tested for their ability to produce and consume a mixture of VFAs (volatile fatty acids) and aromatic compounds (phenols and indoles) under aerobic, fermentative, and anaerobic respiratory conditions with NO3-, Fe(III), Mn(IV), and SO42- serving as anaerobic terminal electron acceptors, over a six-week incubation. The pen soil had significantly higher initial total VFA content (40 umoles g-1 soil) and produced more VFA during incubation than the feedlot ditch soil, while total aromatic compound concentrations were not significantly different between soils. The general pattern of odor compound production and consumption did not differ between soils with respect to treatment. Oxygen and nitrate treatments produced very little VFA and consumed acetate more rapidly than the other treatments, which produced large amounts of short chain VFA and consumed acetate only after all other VFAs were consumed. Aerobic incubation proved most effective with all compounds rapidly con- sumed by the second day of incubation. Of the anaerobic treatments exam- ined, nitrate proved most effective followed by iron, with VFAs consumed by day 5 and 21, respectively. Anaerobic incubation with sulfate or oxidized manganese produced more VFA than the fermentative incubation. Aromatic compounds were more easily consumed aerobically and were only slowly consumed in the anaerobic treatments. We conclude from this study that cattle feedlot soils showed a varying, potentially exploitable capacity for odor consumption when alternate electron acceptors were available.