Interpretive Summary: Contamination of animal tissues with bacteria at slaughter continues to contribute to illnesses in the United States every year. Recent discoveries by ARS scientists have shown that a sodium chlorate used as feed or water additive may help to mitigate contamination of carcasses by reducing the numbers of pathogens in the intestines and feces at slaughter. Reduced populations of pathogens eliminated by animals may help to reduce incidence of carcass contamination. A study was conducted at the ARS Animal Metabolism-Agricultural Chemicals Research Unit in Fargo, ND to help discern how chlorate serves to cleanse live animals of specific bacterial populations. Chlorate administered directly into the blood stream (bypassing the stomach) was as effective at reducing bacterial populations shed in feces as was orally administered sodium chlorate. These results suggest that sodium chlorate may act within the host tissues to make colonization of the gastrointestinal tract more difficult.

Technical Abstract:
The effect of gavage or intravenous (i.v.) administration of sodium chlorate salts on the fecal shedding of generic Escherichia coli in wether lambs was studied. To this end, 9 lambs (27 +/- 2.5 kg) were administered 150 mg NaClO3 per kg BW by gavage or i.v. infusion in a cross-over design with saline-dosed controls. The cross-over design allowed each animal to receive each treatment during one of three trial periods, resulting in 9 observations for each treatment. Subsequent to dosing, jugular blood and rectal fecal samples were collected at 0, 4, 8, 16, 24, and 36 h. Endpoints measured were fecal generic E. coli concentrations; blood packed cell volume, blood methemoglobin concentration, and serum and fecal sodium chlorate concentrations. Sodium chlorate had no effects (P > 0.05) on blood PVC or methemoglobin. Fecal generic E. coli concentrations were decreased (P < 0.05) approximately 2 log units (99%) relative to controls 16 and 24 h after sodium chlorate infusion and 24 h after sodium chlorate gavage. Within, and across, time and treatment, fecal chlorate concentrations were highly variable for both gavage and i.v. lambs. Average fecal sodium chlorate concentrations never exceeded 100 ug/g and were typically less than 60 ug/g from 4 to 24 hours after dosing. Times of maximal average fecal sodium chlorate concentration did not correspond with times of lowered average generic E. coli concentrations. Within route of administration, serum sodium chlorate concentrations were greatest (P < 0.01) 4 hours after dosing; at the same time point, serum chlorate was greater (P < 0.01) in i.v. dosed lambs than gavaged lambs, but not at 16 or 24 h (P > 0.05). At 8 h, serum chlorate concentrations of gavaged lambs were greater (P < 0.05) than in i.v. dosed lambs. Serum chlorate data are consistent with earlier studies indicating very rapid transfer of orally dosed chlorate to systemic circulation and fecal chlorate data are consistent earlier data showing the excretion of low to marginal concentrations of sodium chlorate in orally dosed animals. Efficacy of sodium chlorate at reducing fecal E. coli concentratons after i.v. infusion suggests that low concentrations of chlorate in gastrointestinal contents, delivered by biliary excretion or intestinal cell sloughing, are effective at reducing fecal E. coli levels. Alternatively, the data suggest that chlorate has systemic effects that influence fecal E. coli populations.