To determine the effects on E. coli O157:H7 and Salmonella prevalence and load from feeding a direct fed microbial (DFM) to feedlot cattle. <P>This project will be conducted according to the signed protocol (the 'Protocol'), a copy of which, when available, will be attached to this agreement. The Protocol is incorporated by reference into this agreement.
Approach: ARS will evaluate 512 feedlot cattle in accordance with the Protocol over a 84-day feeding period in the summer of 2007 to determine if feeding the DFM to cattle impacts the E. coli O157:H7 and Salmonella colonization and shedding cycles associated with feedlot cattle. Half of the animals (256 head in eight feedlot pens) will be fed a standard finishing ration containing the DFM. The remaining 256 animals, also in eight pens, will serve as the control group and be fed the same ration without the DFM. Feces and hides from all of the cattle will be screened for E. coli O157:H7 prevalence and level. Then the cattle will be assigned to one of sixteen pens by blocking across pens for prevalence and level of E. coli O157:H7. Hide and fecal samples will be obtained on days 0, 28, 63, and 84. All samples will be processed for prevalence and enumeration of both E. coli O157:H7 and Salmonella. Fecal samples will be collected by rectal palpation. Hide samples will be collected by swabbing 1000 cm2 behind the left shoulder with a sterile sponge. Prevalence data will be statistically analyzed using pen as the experimental unit. Enumeration data will be analyzed using animal as the experimental unit.