Reference | Halbert2006a (20033) (Excluded)

One hundred thirty-two dairy farms were chosen from Michigan, Minnesota, New York, and Wisconsin, from which 128 farms had Campylobacter isolates available for antimicrobial susceptibility testing. Herds were enrolled according to farm type (organic vs conventional) and by farm size (No. of lactating and nonlactating cows). To be included in the study, a farm had to meet the following criteria: have at least 30 milking cows in the herd, have at least 90% of cows in the herd of Holstein breed, raise their own calves for replacement cattle, and ship milk all year. Organic farms had to be certified as organic by a recognized organic certification agency and may not have used antimicrobials in cattle > 1 year old for at least 3 years. Lists of farms were obtained from the respective state departments of agriculture, and herd owners within approximately 100 miles of the respective universities were randomly chosen to receive a mailing describing the study. Owners of farms were asked to indicate interest in participation in the study by returning a postcard. The final list of farms was obtained by randomly choosing names of respondents that had indicated willingness to participate in the study. To evaluate potential herd management practices as risk factors, a predetermined number of farms was enrolled within the following herd size categories: 30 to 49, 50 to 99, 100 to 199, and ≥ 200 cows. Because of the limited availability of organic farms, owners of all known organic farms within approximately 150 miles of the respective universities were contacted to determine eligibility on the basis of selection criteria and their desire to participate in the study. Farm visits for the collection of cattle and environmental samples took place every other month during a 12-month period.

Approximately 10 g of fecal material was collected from the rectum of cattle and placed into plastic bags.b A separate glove was used to collect each sample. The number of samples collected per herd and the number of samples collected from specific cattle groups were determined by herd size. The total number of fecal samples from herds with 30 to 49, 50 to 99, 100 to 199, and ≥ 200 cows was 30, 40, 50, and 55 samples, respectively. Cattle management groups included preweaned heifer calves, cows to be culled within 14 days, periparturient cows (due to calve within 14 days and cows within 14 days in lactation after calving), sick cows as determined by farm personnel or the herd veterinarian, and healthy lactating cows. No effort was made to collect samples from the same individual cattle at subsequent herd visits. Farm environmental samples—One sample from each location was collected at each sampling visit by wiping areas to be tested with sterile gauze pads soaked in double-strength skim milk (skim milk powderc reconstituted with 50% of the volume of water normally used and sterilized via autoclaving), which were placed into plastic bagsb for shipment. Sampling locations included areas in which cattle may be directly exposed to Campylobacter, including feed bunk of lactating cows; lagoon or manure pile; bird droppings in areas housing cows; and the walls, boards, or flooring of maternity pens and areas housing calves or sick cattle. In cows that were going to be culled, a sample was obtained by wiping the coat across the lower aspect of the flank and gluteal region with a swab soaked in double-strength skim milk. If a pen location was not used on a particular farm (eg, no sick pen), then no sample was collected for that location. Samples collected from pens used for more than 1 purpose, such as the sick cow pen and calving pen, were labeled according to the predominant use. A sample from a water source for cattle (eg, a water tank or a pooled swab specimen from 5 drinking cups), a bulk tank milk sample, and a milk line filter were also collected.

AST Method: None

Reference explicitly reports AST breakpoints: True

Reference reports using a MIC table: True