Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 26, 1995
Publication Date: N/A
Technical Abstract: Fermentation in the rumen has the capacity to suppress the growth of most coliform bacteria, including E. coli. Previous work has demonstrated that withholding feed from animals decreases rumen VFA concentrations and increases rumen pH. Under such conditions, normal rumen function is perturbed. When animals are refed after a fast, an opportunity exists for coliform bacteria to transiently expand their populations beyond normal levels. Continued refeeding eventually reestablishes normal rumen function and its capacity for coliform suppression. In current experiments, an intermittent feeding model (fast 48 h, feed once, fast 48 h, feed) was used to demonstrate the effects that fasting stress can have upon fecal shedding of total coliforms, E. coli strain 4910 (a nalidixic acid derivative of an ovine rumen isolate), and an E. coli O157:H7 isolate. In both calves and sheep, the intermittent feeding model increased the fecal shedding of coliforms as compared to normally fed animals. Sheep inoculated with strain 4910 also shed higher levels of this bacterium. Strain 4910 became undetectable on selective medium within 2 wk after resuming normal feeding, but a second intermittent feeding treatment (without reinoculation) resulted in the re-emergence of this strain. Intermittent feeding of calves inoculated with E. coli O157:H7 also resulted in increased fecal shedding. We conclude that erratic feeding can result in increased shedding of enteropathogens that are of a food safety concern. Management practices that contribute to dietary stress during marketing and transport can increase pathogen loads carried by animals just prior to slaughter.