RISK-FACTORS FOR FECAL SHEDDING OF ESCHERICHIA-COLI O157-H7 IN DAIRY CALVES

A case-control study was conducted to determine risk factors for fecal shedding of Escherichia coli O157:H7 (EGO) in dairy calves. Three her ds previously found to lack calves that shed Eco in their feces were s elected for each herd previously found to have calves that shed Eco. F ecal samples from 965 calves on 64 farms were tested for Eco by microb ial culture. Sample prevalence of Eco in calves less than 8 weeks old was 1.4% and in calves 8 weeks or older was 4.8%. Calves were 3 rimes move likely to shed Eco after weaning than before weaning. Shedding of ECO was associated with grouping calves before weaning;feeding whole cottonseed was negatively associated with. ECO shedding. The change in results between testing periods illustrated that an individual herd's status cannot be defined by a single testing of a small sample of cat tle.