Submitted to: ARS Food Safety and Inspection Service Research Workshop
Publication Type: Abstract Only
Publication Acceptance Date: December 12, 1995
Publication Date: N/A
Technical Abstract: Rumen conditions of low pH and high volatile fatty acid (VFA) concentrations in well fed cattle and sheep suppress the growth of E. coli and other coliforms. Previous work shows that withholding feed (48 h) decreases VFA concentrations and increases pH in the rumen; conditions that cause a decrease in rumen anaerobes and perturb normal rumen function. Subsequent refeeding allows coliforms to rapidly increase. We used an intermittent feeding model (fast 48 h, feed, fast 48 h, feed) to examine the effect of dietary stress in sheep and calves on fecal shedding of total coliforms, E. coli strain 4910 (a nalidixic acid resistant derivative of a sheep rumen E. coli isolate), and an E. coli O157:H7 isolate. In both sheep and calves, fecal coliform shedding increased in intermittently fed animals but not in animals fed normally. Intermittent feeding of sheep inoculated with strain 4910 caused high fecal shedding (3 x 10**8 CFU/g) of fthis strain. Strain 4910 was undetectable on selective media (<66 CFU/g) 1-2 wk following resumption of daily feeding. Subsequent intermittent feeding (without reinoculation) caused reemergence of strain 4910 (4 x 10**6 CFU/g). Intermittent feeding of calves experimentally inoculated with E. coli O157:H7 caused increased shedding with some animals having greater than 10**8 CFU/g of feces. These results suggest that animals which are not fed regularly may shed high numbers of enteropathogens in their feces and therefore have implications for management practices of cattle at marketing and slaughter.