Antimicrobial Use on 36 Beef Feedlots in Western Canada: 2008-2012

Abstract

The accurate quantification of antimicrobial use (AMU) in production animals is critical for monitoring trends in exposure to antimicrobial drugs (AMD) over time and examining potential associations with antimicrobial resistance in bacteria. In this study, a census sample of cattle was used to quantify individually-dosed and in-feed AMU as both numbers of animal daily doses (nADD) and total grams of AMD (gAMD) used in cattle placed in 36 western Canadian feedlots between 1-November, 2008 and 31-October, 2012; representing about 21.5% of fed cattle in Canada during that time period. Of the ~2.6 million cattle placed during the 48-month period, 45% were calves, 63% were male, 62% arrived in the fall or winter, and 39% were assessed as high risk for developing bovine respiratory disease (BRD). The proportion of cattle categorized as high risk (HR) for developing BRD was consistent over the 4 years of placement cohorts. Both medically important AMU and ionophore use were summarized but presented separately. A decrease in AMU was observed over the study period, both as nADD and total gAMD, which was primarily driven by a decline in the in-feed administration of tetracyclines. Most in-feed AMU was directed toward prevention and control of liver abscesses. The majority of individually dosed AMU was administered as metaphylaxis to address BRD risks, with category III AMD (medium importance to human medicine as categorized by Health Canada Veterinary Drugs Directorate) used most frequently. Not surprisingly, risk level for developing BRD influenced parenteral AMD exposures, with 95% of cattle categorized as being HR for developing BRD receiving individually dosed AMD compared to 59% of cattle categorized as being low risk (LR) for developing BRD. Cattle categorized as HR for developing BRD were more likely to receive macrolides for BRD metaphylaxis compared to cattle categorized as LR for developing BRD, and cattle categorized as LR for developing BRD were more likely to receive tetracycline for the same purpose. In summary, these data provide an unprecedented representation of AMU in fed cattle in western Canada and direction for future monitoring of AMU in fed cattle.

Keywords: Canada; antimicrobial use; bovine respiratory disease; feedlot cattle; quantification.

Figure 1

(A) Individually dosed and in-feed antimicrobial drug use (AMU) in number of animal daily doses (nADD)/100,000 cattle in placement cohort^a (PC), cattle placed 2008–2012. (B) Individually dosed and in-feed antimicrobial drug use in total grams of antimicrobial drug (gAMD)/100,000 cattle in placement cohort^a (PC), cattle placed 2008–2012. ^aPlacement cohort comprised of cattle placed in the feedlot between 1 November and 31 October of consecutive years.

Figure 2

(A) Individually dosed antimicrobial drug use in nADD/100,000 cattle by placement cohort (PC)^a, antimicrobial class^b, and specific type of antimicrobial drug^c, cattle placed 2008–2012. (B) Individually dosed antimicrobial drug (AMD) use in grams AMD (gAMD)/100,000 cattle by placement cohort (PC)^a, antimicrobial class^b, and specific type of antimicrobial drug^c, cattle placed 2008–2012. ^aPlacement cohort comprised of cattle placed in the feedlot between 1 November and 31 October of consecutive years. ^bMAC, macrolides; TET, tetracyclines; CEPH, third generation cephalosporins; FQ, fluoroquinolones; PHEN, phenicols (TMS, trimethoprim-sulfamethoxazole; PEN, penicillin; SULF, sulfonamides not depicted due to low usage; ^cTIL, tilmicosin 10 mg/kg; TUL, tulathromycin 2.5 mg/kg; OTHMAC, gamithromycin 6 mg/kg, tildipirosin 4 mg/kg, tylosin 29 mg/head; TET100, oxytetracycline 6.67 mg/kg; TET200, oxytetracycline 20 mg/kg; TET300, oxytetracycline 30 mg/kg; CEF1, ceftiofur hydrochloride or sodium, 1.1 mg/kg; CEF6, ceftiofur crystalline free acid 6.6 mg/kg; DANO, danofloxacin 6 mg/kg; ENRO, enrofloxacin 7.7 mg/kg; FLOR, florfenicol 40 mg/kg.

Figure 3

(A) In-feed antimicrobial drug use in nADD/100,000 cattle by placement cohort (PC)^a, and antimicrobial class^b, cattle placed 2008–2012. (B) In-feed antimicrobial drug use in grams AMD (gAMD)/100,000 cattle by placement cohort (PC)^a, and antimicrobial class^b, cattle placed 2008–2012. ^aPlacement cohort comprised of cattle placed in the feedlot between 1 November and 31 October of consecutive years. ^bCTC, chlortetracycline; OTC, oxytetracycline; TY, tylosin.