Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 11/14/1995
Publication Date: N/A
Technical Abstract: In simulating pre-slaughter livestock feeding schedules and stress, we studied the interaction between the ability to mount an inflammatory response and fecal coliform shedding in cattle harboring Escherichia coli 0157:H7. Minor fasting has been shown to change rumen pH and volatile fatty acid levels; thus, optimizing conditions for E. coli 0157:H7 7growth. Glucocorticoids induce neutrophils to shed L-selectin (CD62L), thus reducing the efficiency of normal inflammatory responses. We monitored CD62L during each experiment to see if loss of CD62L on neutrophils was correlated with increased fecal coliform shedding. Twelve Holstein calves, 4-6 months old, were inoculated with 10**7-10**10 cfu E. coli 0157:H7 and subjected to a fluctuating feeding schedule over 5 days, after which they were returned to a normal feeding schedule. Eight of these calves were then given a single injection of dexamethasone (0.04 mg/kg, IM) after a 2-week rest. We found that dietary stress and dexamethasone increased fecal coliform shedding (including E. coli 0157:H7) and that neutrophil CD62L expression was only affected by dexamethasone administration. Within 24 hours, dexamethasone depressed the proportion of neutrophils bearing CD62L by approximately 75%. A stress leukogram was observed during both fasting and dexamethasone treatments.