title: The effect of antimicrobial treatment and preventive strategies on bovine respiratory disease and genetic relatedness and antimicrobial resistance of Mycoplasma bovis isolates in a western Canadian feedlot.
abstract: Feedlot calves (n = 3784) were systematically randomized and allocated in a 2 × 2 factorial study to receive metaphylactic oxytetracycline (OTC) on arrival or no antimicrobial, as well as florfenicol once subcutaneously or twice intramuscularly (48 h apart) if diagnosed with bovine respiratory disease (BRD). Calves of different treatment groups were comingled and followed from placement to re-implantation (~100 days). Animals receiving OTC had a reduced risk of BRD, an increased risk of arthritis, and no significant differences in average daily gain, BRD relapse, overall mortality, or BRD mortality. There were no significant differences between treatment protocols. Deep nasal swabs (n = 233) taken at arrival (n = 122), treatment (n = 77), and swabs from lungs and joints at postmortem (n = 34) were cultured for Mycoplasma bovis from 61 animals ill or dying of chronic pneumonia and arthritis and from 61 healthy calves. There was significant variation in diversity among isolates (n = 51) between study years and different cattle. Metaphylaxis or antimicrobial treatment did not affect the diversity of isolates. Except for tilmicosin, isolates were largely susceptible to tested antimicrobials.
authors.affiliation: Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4 (Hendrick); Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1 (Bateman); Rosengren Epidemiology Consulting Ltd., Box 451, Midale, Saskatchewan S0C 1S0 (Rosengren).
authors.forename: Steven H
authors.initials: SH
authors.lastname: Hendrick
authors.forename: Ken G
authors.initials: KG
authors.lastname: Bateman
authors.forename: Leigh B
authors.initials: LB
authors.lastname: Rosengren
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001168:Arthritis / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary; D048090:Bovine Respiratory Disease Complex / Q000188:drug therapy / Q000382:microbiology / Q000517:prevention & control*; D002417:Cattle; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005260:Female; D008297:Male; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D009175:Mycoplasma Infections / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary*; D045682:Mycoplasma bovis / Q000187:drug effects* / Q000235:genetics; D010118:Oxytetracycline / Q000627:therapeutic use*; D012525:Saskatchewan; D013839:Thiamphenicol / Q000031:analogs & derivatives / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; C035534:florfenicol; D013839:Thiamphenicol; D010118:Oxytetracycline