ARS | Publication request: Laboratory Study of Oxytetracycline Degradation Kinetics in Animal Manure and Soil

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 2008
Publication Date: February 8, 2008
Citation: Wang, Q., Yates, S.R. 2008. Laboratory Study of Oxytetracycline Degradation Kinetics in Animal Manure and Soil. Journal of Agricultural and Food Chemistry. Vol 56: 1683-1688

Interpretive Summary: Veterinary antibiotics are widely used in confined animal operations to treat disease, protect the health of animals, and to improve growth rate. About 21.9 million pounds of antibiotics were administered annually in the U.S. to farm and companion animals from 2002 to 2004. Disposal of contaminated manure is problematic and has gained increasing attention from both the public and the scientific community. One proposal is to apply the manure to agricultural lands. This may be an effective and feasible means to utilize manure as a soil amendment, but information is needed to ensure that veterinary antibiotics are not released into the environment. In the present study, the degradation of oxytetracycline in manure under laboratory aerobic incubation conditions was investigated. Experimental data were fitted using an availability-adjusted first-order kinetic model. The effect of manure moisture, temperature, and the presence of other antibiotics was examined. The degradation in manure was compared to degradation in soil. The results indicate that oxytetracycline may become much more persistent in the environment once it is released from the contaminated manure and may accumulate in soil after cyclic application of contaminated manure. Optimal storage management during storage and composing can help to diminish oxytetracycline concentrations by utilizing high temperatures and moderately high moisture under aerobic conditions.

Technical Abstract: As a major member of tetracyclines, oxytetracycline (OTC) is widely administered to animals in confined feeding operations. To diminish the contamination of OTC in the environment resulting from the application of OTC-contained manure as fertilizers to agriculture lands, OTC degradation kinetics in manure and soil under laboratory aerobic conditions was investigated. It was found that OTC degradation kinetics were described well by an availability-adjusted first-order model at all moistures and low temperatures (<= 25oC). OTC degradation increased as moisture increased from 60 to 100%. However, OTC became very persistent in water-saturated manure. Increasing temperature greatly accelerated OTC degradation and thermal degradation became significant at high temperatures (>= 35oC) in manure. At 25oC, OTC half-life was determined to be 8.1 d in manure with 80% moisture, and 33 and 56 d, respectively, in manure-amended (amendment ratio at 5%) and non-amended soil with 20% moisture. This demonstrates that OTC may become persistent in the environment once it is released from manure into soil. The coexistence of other antibiotics in manure exhibited no significant effect on OTC degradation.