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The purpose of our mail survey was to compare the adoption of management practices recommended for Johne's disease (JD) control between herds involved in whole-herd testing programs versus those that do not routinely test the entire herd for JD. A questionnaire consisted of 38 closed-ended questions that inquired about: general herd characteristics; management practices related to JD control; changes that occurred within the last 5 years regarding management practices recommended for the control of JD; producer knowledge of JD; the perceived infection status of the herd by the producer; and herd JD-testing history. The questionnaire was mailed to 810 Ohio dairy producers in September 2002; 266 questionnaires were returned (32.8% response). We used univariable logistic-regression models to assess the relationship between whole-herd testing status (TESTING versus NON-TESTING) and each management practice, each change in management practice and producer knowledge about JD. Because it is conceivable that only producers who believe their herds to be infected would be motivated to adopt the management practices recommended for control of JD, the comparisons were repeated with models that controlled for producer-perceived infection status. Of the 20 management practices recommended for JD control that we evaluated, 7 differed between TESTING and NON-TESTING herds. Additionally, TESTING herds more-frequently reported adopting changes within the past 5 years relative to NON-TESTING herds with respect to 7 of 9 management practices evaluated. Producers with TESTING herds also reported greater familiarity with JD than those with NON-TESTING herds.

Factor analysis was used to assess relationships in the minimum-inhibitory concentration among 17 antimicrobials tested on isolates of Escherichia coli isolated from 360 faecal samples obtained from feedlot cattle. Six factors were extracted using maximum-likelihood factor analysis. The factors were interpretable antimicrobial groupings based on class of antimicrobial and previously described associations. New-generation cephalosporins, older-generation beta-lactams, fluoroquinolones and aminoglycosides grouped separately as classes of antimicrobials on four of the six factors. One of the remaining factors was a grouping of antimicrobials that had been identified as being related in previous feedlot studies. The last factor was a grouping of three of the five antimicrobials that comprise the antimicrobials found in penta-resistant strains of Salmonella Typhimurium. The factor analysis described patterns in the MIC data that would not have been apparent if only antimicrobial-resistance data categorized as susceptible-resistance had been analysed.

Objective: To evaluate the effectiveness of various sampling techniques for determining antimicrobial resistance patterns in Escherichia coli isolated from feces of feedlot cattle., Sample Population: Fecal samples obtained from 328 beef steers and 6 feedlot pens in which the cattle resided., Procedure: Single fecal samples were collected from the rectum of each steer and from floors of pens in which the cattle resided. Fecal material from each single sample was combined into pools containing 5 and 10 samples. Five isolates of Escherichia coli from each single sample and each pooled sample were tested for susceptibility to 17 antimicrobials., Results: Patterns of antimicrobial resistance for fecal samples obtained from the rectum of cattle did not differ from fecal samples obtained from pen floors. Resistance patterns from pooled samples differed from patterns observed for single fecal samples. Little pen-to-pen variation in resistance prevalence was observed. Clustering of resistance phenotypes within samples was detected., Conclusions and Clinical Relevance: Studies of antimicrobial resistance in feedlot cattle can rely on fecal samples obtained from pen floors, thus avoiding the cost and effort of obtaining fecal samples from the rectum of cattle. Pooled fecal samples yielded resistance patterns that were consistent with those of single fecal samples when the prevalence of resistance to an antimicrobial was > 2%. Pooling may be a practical altemative when investigating patterns of resistance that are not rare. Apparent clustering of resistance phenotypes within samples argues for examining fewer isolates per fecal sample and more fecal samples per pen.