Monitoring Escherichia coli O157:H7 in Inoculated and Naturally Colonized Feedlot Cattle and Their Environment
On-farm methods of monitoring Escherichia coli O157:H7 were assessed in 30 experimentally inoculated steers housed in four pens over a 12-week period and in 202,878 naturally colonized feedlot cattle housed in 1,160 pens on four commercial Alberta feedlots over a 1-year period.
In the challenge study, yearling steers were experimentally inoculated with 1010 CFU of a four-strain mixture of nalidixic acid–resistant E. coli O157:H7. After inoculation, shedding of E. coli O157:H7 was monitored weekly by collecting rectal fecal samples (FEC),
oral swabs (ORL), pooled fecal pats (PAT), manila ropes (ROP) orally accessed for 4 h, feed samples, water, and water bowl interface. Collection of FEC from all animals per pen provided superior isolation (P < 0.01) of E. coli O157:H7 compared with other methods, although
labor and animal restraint requirements for fecal sample collection were high. When one sample was collected per pen of animals, E. coli O157:H7 was more likely to be detected from the ROP than from the FEC, PAT, or ORL (P < 0.001). In the commercial feedlot study, samples
were limited to ROP and PAT, and E. coli O157:H7 was isolated in 18.8% of PAT and 6.8% of ROP samples. However, for animals that had been resident in the feedlot pen for at least 1 month, isolation of E. coli O157:H7 from ROP was not different from that from PAT (P = 0.35).
Pens of animals on feed for < 30 days were six times more likely to shed E. coli O157:H7 than were animals on feed for > 30 days. However, change in diet did not affect shedding of the organism (P < 0.23) provided that animals had acclimated to the feedlot for 1 month
or longer. Findings from this study indicate the importance of introduction of mitigation strategies early in the feeding period to reduce transference and the degree to which E. coli O157:H7 is shed into the environment.
Document Type: Research Article
Alberta Agriculture, Food and Rural Development, Agriculture Centre, 5401 1st Avenue S., Lethbridge, Alberta, Canada T1J 4V6
Agriculture and Agri-Food Canada, Research Centre, Box 3000, Lethbridge, Alberta, Canada T1J 4B1
Alberta Agriculture, Food and Rural Development, 7000 113th Street, Edmonton, Alberta, Canada T6H 5T6
Alberta Agriculture, Food and Rural Development, Provincial Building, 5030 50th Street Olds, Alberta, Canada T4H 1S1
Alberta Agriculture, Food and Rural Development, Provincial Building, Box 670, Cardston, Alberta, Canada T0K 0K0
Publication date: January 1, 2005
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