Davedow, Taylor and Narvaez-Bravo, Claudia and Zaheer, Rahat and Sanderson, Haley and Rodas-Gonzalez, Argenis and Klima, Cassidy and Booker, Calvin W. and Hannon, Sherry J. and Bras, Ana L. and Gow, Sheryl and McAllister, Tim (Canada)
None (2020)
7,576 crossbred beef yearling steers and heifers (394 ± 5.49 kg) and cattle were randomly assigned to one of three treatments; FIRST-78%, LAST-75%, or CON. The experimental unit was the pen, with 10 pens (six steer, four heifer) allocated to each treatment. Average pen capacity was 253 ranging from 246 to 280 head/pen. Cattle were fed tylosin phosphate (Tylosin 40, Bio Agri Mix LP, Mitchell, ON) at an inclusion level of 11 ppm [100% dry matter basis [DM]] for: (1) the first 125 days of the 161-days feeding period (FIRST-78%), (2) the last 120 days of the feeding period (LAST-75%), starting at an average of 41 days on feed (DOF) and continuing to slaughter at an average of 161 DOF, or (3) continuously throughout the 161-days feeding period (CON). The study measured antimicrobial resistance, liver abscess score, animal health, feedlot performance, and carcass traits of feedlot cattle.
Composite, fresh, pen-floor fecal samples from 20 different pats were collected from each pen using a standardized pen sampling plan. Samples were collected at allocation (0 DOF) before any tylosin was administered, in the middle of the feeding period (avg. 81 DOF), and just prior to shipment for slaughter (avg. 160 DOF). Samples were cultured on a combination of both non-selective and erythromycin selective media.
AST Method: None
Reference explicitly reports AST breakpoints: False
Reference reports using a MIC table: False
Is Excluded: False
| Country | Sub-Region | Sub-Region Detail |
|---|---|---|
| Canada | Alberta (Province) | Large commercial feedlot in southern Alberta |
| ID | Note | Resolution |
|---|
| Title | Host | Host | Production Stage | Description | ROs |
|---|---|---|---|---|---|
| In-feed Tylosin | Cattle | Beef Heifers and Steers | Feedlot | Cattle were fed 11ppm tylosin phosphate in feed for the first 125 days of the 161-days feeding period (FIRST-78%). Samples were cultured on a combination of both non-selective and erythromycin selective media. | 8 |
| In-feed Tylosin | Cattle | Beef Heifers and Steers | Feedlot | Cattle were fed 11ppm tylosin phosphate in feed for the last 120 days of the 161-days feeding period (LAST-75%). Samples were cultured on a combination of both non-selective and erythromycin selective media. | 8 |