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The effects of feed or water administration of experimental chlorate preparations on recovery of generic Escherichia coli and E. coli O157:H7 from the gut, hide and carcasses of feedlot cattle were tested. Sixty-four naturally colonized cattle were randomly assigned to one of four feed treatments with or without a 12 h chlorate-containing water treatment. An analysis of variance revealed a main effect of feed treatment ( P = 0.002 ) on generic E. coli concentrations in feces collected before shipment to slaughter. Main effect means were 5.57, 4.75, 5.00 and 4.08 log10 cfu/g for animals fed an experimental chlorate product at 0, 0.01% in last meal, 0.01% for last 5 d and 0.05% of body weight in last meal, respectively. A main effect of feed treatment was observed ( P = 0.041 ) on generic E. coli concentrations in feces collected at slaughter (means for the respective treatments were 4.92, 3.57, 3.98 and 3.20 log10 cfu/g) as well as on numbers of generic E. coli recovered ( P = 0.034 ) from hide swabs collected at the rump (means for the respective treatments were 4.86, 3.92, 3.87 and 4.06 log10 cfu/swab). A main effect of water treatment was observed ( P 0.016 ) on generic E. coli concentrations in rumen contents (3.44 vs. 2.72 cfu log10 cfu/g for animals administered 0 or 2500 ppm active chlorate ion, respectively). Logistic regression analysis revealed a main effect of feed treatment ( P 0.001 ) on the incidence of E. coli O157:H7 recovered from feces collected at slaughter (75%, 33%, 20% and 25% for animals fed an experimental chlorate product at 0%, 0.01% in last meal, 0.01% for last 5 d and 0.05% of body weight in last meal, respectively). Animals exhibited no symptoms of chlorate toxicity and negative effects on feed or water intake or animal performance were not observed. |
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