Effects of experimental chlorate preparations as feed and water supplements on Escherichia coli colonization and contamination of beef cattle and carcasses

摘要

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 log_(10) 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 log_(10) 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 log_(10) 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 log_(10) 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.