Antimicrobial use quantification in adult dairy cows – Part 2 – Developing a foundation for pharmacoepidemiology by comparing measurement methods

Nora Schrag, Michael D. Apley, Sandra M Godden, Randall Singer, Brian Lubbers

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


As stewardship programmes seek to influence therapeutic choices and reduce resistance selection pressure, it is essential to understand the multiple factors which may influence any given antimicrobial use measure. This article compares 9 measures of antimicrobial use pertaining to adult cows in US dairy systems based on treatment records standardized to a single standardized regimen (SReg) format. There are 3 fundamental parameters underlying the nine measures: amount of active substance (AMOUNT), number of SRegs (ANIMALS) and treatment time (TIME). Additionally, three use categories were considered in the analysis: control of mastitis (Dry Cow), treatment of detected mastitis (Clinical Mastitis) and treatment of other diseases (Other Treatment). The assumptions necessary for calculation of each of the nine measures are identified. The influence of measure choice on farm rank was explored at the farm level both within and across fundamental parameters. Across all use categories, when measures of TIME and ANIMALS were compared, correlations between measures were greater than 0.91. However, when measures of AMOUNT were compared to either measures of TIME or ANIMALS, the correlation between measures was more variable across use categories (R = 0.31–0.91). These comparisons demonstrate that the selection of antimicrobial use metric can affect which dairies are considered the highest users of antimicrobials. Measurement selection also influences which use category has the greatest potential for use reduction. This indicates that measure selection can influence which use category is prioritized as a target for reduction of antimicrobial use. Utilization of this information may allow those developing dairy antimicrobial stewardship programmes to better understand the potential effects of measurement selection on driving changes in antimicrobial use.

Original languageEnglish (US)
Pages (from-to)69-81
Number of pages13
JournalZoonoses and Public Health
Issue numberS1
StatePublished - Nov 17 2020

Bibliographical note

Funding Information:
Thank you to the producers who volunteered their time, data and expertise in helping to identify relationships between antimicrobial use measures and their potential confounders. Collaboration on data management and analysis was provided by the Center for Epidemiology and Animal Health (CEAH) at USDA:APHIS:VS in Fort Collins, Colorado. Funding for this project was made possible, in part, by the U.S. Food and Drug Administration through grant number U01FD005868. Views expressed do not necessarily reflect the official policies of the Department of Health and Human Services; nor does any mention of trade names, commercial practices or organization imply endorsement by the United States Government. Special thanks to Dr. Kathe Bjork (USDA‐APHIS CEAH) and Dr. Susan Bright and Dr. Anna Nevius (FDA) for collaborations on data management and review of the manuscript.

Publisher Copyright:
© 2020 Wiley-VCH GmbH


  • antibacterial agents
  • days of therapy
  • defined daily dose
  • drug utilization
  • pharmacoepidemiology
  • resistance

PubMed: MeSH publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Journal Article


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