Comparative efficacy of antimicrobial treatments in dairy cows at dry-off to prevent new intramammary infections during the dry period or clinical mastitis during early lactation: a systematic review and network meta-analysis.

C B Winder,C Moody,T F Duffield,K J Churchill,K Dawkins,J M Sargeant,D F Kelton,A M O'Connor,H Wood,C Wang,M D Bergevin,S J Leblanc,S Meadows,J Glanville,B Deb,J Dunn,D Hu,M Reist

doi:10.1017/s1466252319000239

Abstract

A systematic review and network meta-analysis were conducted to assess the relative efficacy of antimicrobial therapy given to dairy cows at dry-off. Eligible studies were controlled trials assessing the use of antimicrobials compared to no treatment or an alternative treatment, and assessed one or more of the following outcomes: incidence of intramammary infection (IMI) at calving, incidence of IMI during the first 30 days in milk (DIM), or incidence of clinical mastitis during the first 30 DIM. Databases and conference proceedings were searched for relevant articles. The potential for bias was assessed using the Cochrane Risk of Bias 2.0 algorithm. From 3480 initially identified records, 45 trials had data extracted for one or more outcomes. Network meta-analysis was conducted for IMI at calving. The use of cephalosporins, cloxacillin, or penicillin with aminoglycoside significantly reduced the risk of new IMI at calving compared to non-treated controls (cephalosporins, RR = 0.37, 95% CI 0.23-0.65; cloxacillin, RR = 0.55, 95% CI 0.38-0.79; penicillin with aminoglycoside, RR = 0.42, 95% CI 0.26-0.72). Synthesis revealed challenges with a comparability of outcomes, replication of interventions, definitions of outcomes, and quality of reporting. The use of reporting guidelines, replication among interventions, and standardization of outcome definitions would increase the utility of primary research in this area.

Highlights

The majority of antimicrobial use in the dairy industry is for the treatment and prevention of intramammary infections (IMI); in the Netherlands, approximately 60% of all antimicrobial use in dairy is for this purpose, with two-thirds being dry cow therapy (Lam et al, 2012)
From an initial 3480 articles screened by title and abstract, 756 full texts were reviewed, with 697 not meeting full-text eligibility criteria, and 59 studies including 75 trials included after full-text screening
Of these 75 clinical trials, 35 had data that were not usable

Summary

Introduction

RationaleThe majority of antimicrobial use in the dairy industry is for the treatment and prevention of intramammary infections (IMI); in the Netherlands, approximately 60% of all antimicrobial use in dairy is for this purpose, with two-thirds being dry cow therapy (Lam et al, 2012). In the United States, over 90% of dairy cows receive dry cow therapy after every lactation (USDA-APHIS, 2016), with the goal of treating or preventing IMI during the dry period. In the United States, clinical mastitis represents the most common disease treated with antimicrobials in adult dairy cows, with approximately 16% of cows reported as having been treated in 2007, with cephalosporins the most commonly used drug class (United States Department of Agriculture, 2008). To reduce IMI during the dry period, blanket dry cow therapy (intramammary antimicrobial administration to all quarters of all cows after the last milking of the lactation) has been recommended for decades (Neave et al, 1969), and has been widely adopted in North America and the United Kingdom (Ruegg, 2017).

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