In a series of five experiments, we evaluated the effect of chlorate on reducing gut populations of the E. coli capable of causing post-weaning diarrhea. In three of the experiments, we had a model using pigs that broke naturally with post-weaning diarrhea. We administered the chlorate by oral gavage and looked at several treatment times in an attempt to determine which time would be most effective in reducing gut populations of E. coli. Surprisingly, we did not see any effect of chlorate on gut populations or on the incidence of scours. Other researchers in our laboratory have seen a reduction of E. coli in chlorate-treated pigs using similar methodology. Increasing the dosing frequency of chlorate or including chlorate in the water, may be a more beneficial treatment method to reduce gut populations of E. coli in weaned pigs.