Abstract
Monitoring antimicrobial usage (AMU) in dairy cattle is becoming common in a growing number of countries, with the ultimate goal to improve practices, reduce the development of antimicrobial resistance, and protect human health. However, antimicrobials delivered as feed additives can be missed by some of the quantification methods usually implemented. Our objective was to compare three methods of quantification of in-feed AMU in Québec dairy herds. We recruited 101 dairy producers for one year in the Québec province. Quantities of antimicrobials were calculated by farm from: (1) feed mills invoices (reference method); (2) veterinary prescriptions; and (3) information collected during an in-person interview of each producer. We standardized AMU rates in kilograms per 100 cow-years and compared the reference method to both alternative methods using concordance correlation coefficients and Bland–Altman plots. Antimicrobial usage was well estimated by veterinary prescriptions (concordance correlation coefficient (CCC) = 0.66) or by the approximation using producer’s data (CCC = 0.73) when compared with actual deliveries by feed mills. Users of medically important antimicrobials for human medicine (less than 10% of the farms) were easily identified using veterinary prescriptions. Given that veterinary prescriptions were mostly electronic (90%), this method could be integrated as part of a monitoring system in Québec.
Highlights
Different methods of quantification could be used to report on antimicrobial usage (AMU) in medicated feed in dairy farms: (i) quantities sold and delivered by feed mills to dairy farms; (ii) quantities prescribed by veterinarians; and (iii) quantities approximated from information collected directly from dairy producers
A total of 73% of dairy farms (74/101) had at least one medicated feed sold and delivered by one of the 31 feed mills identified during the timeframe of the project
We showed that quantification of AMU in medicated feed was feasible using veterinary prescriptions and found a substantial agreement with the quantification using feed mill invoices
Summary
In-feed antimicrobials are given to livestock animals for the prevention or treatment of diseases, and, in some countries, as growth promotors for improvement in feed efficiency and weight gain [1,2]. With the current concern of residues from antimicrobials excreted in the environment and the emergence of antimicrobial resistance related to antimicrobial usage (AMU) in production animals, knowing how antimicrobials are used in animal feed is crucial [3]. In 2018, growth promotion claims were removed in Canada from drug labels [4] for medically important antimicrobials (MIA) as defined by the World Health Organization [5]. Because coccidiostats (ionophores and others) are not MIA, they were not targeted by this ban and can still be used as growth promotors. For the dairy industry in Canada, only three classes of antimicrobials are found in drug premixes authorized for use in feed:
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