Reference | Funk2006 (10190)

A convenience sample of three swine farms was enrolled in the study on the basis of the following criteria: (1) willingness to alter feed medication; (2) all-in, all-out production from far-row to finish (a farm that comprises all stages of swine pro-duction that age segregates groups of pigs with barns cleaned and disinfected between groups), and (3) willingness to share antimicrobial treatment and growth performance records. Farm 1 enrolled 12 barns, farm 2 enrolled two barns, and farm 3 enrolled eight barns. Within each farm, barns were entered into the trial weekly and alternately assigned to one of two groups (treatment or control). Treatment was inclusion of 50g of chlortetracycline per ton (U.S.) of feed for the entire finisher period (~10 weeks of age until ~24 weeks of age). The control group received no antimicrobials in the diet. Other than chlortetracycline, there were no differences within farms between treatment groups in the diets. Farms 1 and 3 used no other antibiotics during the trials. Farm 2 used preventive and therapeutic antibiotics during the trial, and usage patterns were the same in treatment and control barns. In the first week of placement, both treatment and control barns for farm 2 received tiamulin (35 g/ton of complete feed) and chlortetracycline (400 g/ton of complete feed)for 7 days. For days 8–21 of placement, both barns received lincomycin in the feed at 200g/ton of complete feed. After that point, the treatment barn received the 50 g/ton of chlortetracycline in the feed and the control barn included no antibiotics inthe feed. In response to a respiratory disease outbreak between 2 and 3 weeks post-placement, both barns at farm 2 were treated with oxytetracycline in the water and approximately 10% of the pigs were treated individually via intramuscular injection with ceftiofur according to veterinary prescription.

Fecal sampling was conducted within 1 month of marketing for all barns. Sampling was conducted on the same day for each temporally matched treatment and control barn pair within farms. Therefore, two barns (one treatment and one control) would be collected within a sampling day. In each barn, fecal samples (~10 g) were collected from the rectums of 96 individual pigs using a gloved hand, with clean gloves used for each pig. The numbers of fecal samples were equally distributed between the pens in each barn.

AST Method: Agar Dilution

Reference explicitly reports AST breakpoints: True

Reference reports using a MIC table: False