METABOLIC VARIABLES AFFECTING THE EFFICACY, SAFETY, AND FATE OF AGRICULTURAL CHEMICALS
Location: Animal Metabolism-Agricultural Chemicals Research
Title: Fate of chlorate present in cattle wastes and its impact on Salmonella typhimurium and E. coli 0157:H7
Submitted to: Journal of Agricultural Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 28, 2008
Publication Date: July 1, 2008
Citation: Oliver, C.E., Magelky, B.K., Bauer, M., Cheng, F., Caton, J.S., Hakk, H., Larsen, G.L., Anderson, R.C., Smith, D.J. 2008. Fate of chlorate present in cattle wastes and its impact on Salmonella typhimurium and E. coli 0157:H7. Journal of Agricultural Chemistry 56:6573-6583.
Interpretive Summary: Chlorate salts are being developed as a feed additive to reduce the numbers of harmful bacteria in live cattle. A series of studies was conducted to determine whether chlorate would also reduce the populations of harmful bacteria in cattle wastes (a mixture of urine and feces) and to determine the fate of chlorate after excretion from cattle. Chlorate salts present in manure had no significant effects on two harmful bacterial species, E. coli O157:H7 and Salmonella Typhimurium, probably because chlorate was very rapidly degraded and because relatively low concentrations of chlorate salts were used relative to concentrations that have been shown to kill harmful bacteria in live animals. Chlorate degradation was slowest with low temperatures (5 ºC) and the fastest at the highest temperatures (30 ºC) tested; nevertheless, even at cool temperatures chlorate degradation occurred in significant quantities. From an environmental standpoint, chlorate use in feedlot cattle would likely have minimal impacts because any chlorate that escaped degradation on the feedlot floor would be degraded in lagoon systems. Collectively our results suggest that the use of chlorate as a food safety tool would be environmentally friendly.
Chlorate salts are being developed as a feed additive to reduce the numbers of pathogens in feedlot cattle. A series of studies was conducted to determine whether chlorate, at concentrations expected to be excreted in urine of dosed cattle, would also reduce the populations of pathogens in cattle wastes (a mixture of urine and feces) and to determine the fate of chlorate in cattle wastes. Chlorate salts present in a urine-manure-soil mixture at 0, 17, 33, and 67 ppm had no significant effects the rates of E. coli O157:H7 or Salmonella Typhimurium depletion from batch culture studies. Chlorate was rapidly degraded when incubated at 20 and 30 ºC with half-lives of 0.1 to 4 d. Chlorate degradation in batch cultures was slowest at 5 ºC with half-lives of 2.9 to 30 d. The half-life of 100 ppm chlorate in an artificial lagoon system charged with slurry from a feedlot lagoon was 88 h. From an environmental standpoint, chlorate use in feedlot cattle would likely have minimal impacts because any chlorate that escaped degradation on the feedlot floor would be degraded in lagoon systems. Collectively, these results suggest that chlorate administered to cattle and excreted in wastes would have no significant secondary effects on pathogens present in mixed wastes on pen floors. Lack of chlorate efficacy was likely due to low chlorate concentrations in mixed wastes relative to chlorate levels shown to be active in live animals, and the rapid degradation of chlorate to chloride at temperatures of 20 ºC and above.