Reference | McDermott2005 (10058) (Excluded)

Day-old broiler chicks were purchased from a commercial supplier and were raised on corncob bedding at a population density of 1.5 ft2 per bird. In each trial, birds were randomly assigned to two groups (treatment and control) and placed in adjacent floor pens separated by about 3 feet. Both groups were fed a standard broiler starter/ finisher diet that was prepared on site for each new flock. The treatment group received 20g/ton of virginiamycin in the feed, and the control group received nonmedicated feed. Between trials, litter was manually turned and supplemented with fresh litter but was not removed from the pens. We conducted four consecutive feeding trials with groups of broiler chickens raised on the same litter. In trial 1, birds placed on the original litter were allowed to acclimate for 5 days before virginiamycin was introduced into the feed of the treatment group. In trials 2 and 3, day-old broiler chicks in the treatment group were fed virginiamycin-supplemented feed upon arrival and continuously throughout the production cycle. In the fourth and final trial, virginiamycin was excluded from the feed of both treatment and control pens so that the persistence of SREF could be examined in the absence of drug.

In each feeding trial, broiler fecal samples were collected from birds at 1 day of age and again at approximately 1, 3, 5, and 7 weeks of age. Swabs were used to collect fecal material from the cloacae of 25 randomly selected birds from each pen on each sampling date.

AST Method: Broth Microdilution

Reference explicitly reports AST breakpoints: True

Reference reports using a MIC table: False