Abstract
This systematic review and network meta-analysis aimed to estimate the relative efficacy of dry cow antimicrobial therapies, registered in Canada and/or the United States, to cure existing intramammary infections (IMI) in dairy cattle. The controlled trials examining all-cause cures of existing IMI present at dry-off were eligible. Five databases and four conference proceeding platforms were searched. The risk of bias at the level of the outcome was assessed using the Cochrane 2.0 risk of bias instrument (Cochrane, Denmark), and the overall confidence in the findings from the network meta-analysis was assessed using the Confidence in Network Meta-Analysis (CINeMA) platform. Of 3,743 articles screened for eligibility by the two independent reviewers, 58 trials were included in the Bayesian network meta-analysis for the all-cause cure of existing IMI from dry-off to calving. No antimicrobial treatment (non-active control) was associated with a decreased risk of a cure compared with all other currently labeled antimicrobials in Canada and the United States; however, lack of replication trials for some antimicrobial products created large credibility intervals and, therefore, we were unable to identify meaningful comparisons between the products. Poor reporting of trial features, heterogeneity in outcome measurements, and high risk of bias in some domains further contributed to this inability to compare antimicrobials. Continued improvement in the reporting of animal trials is required to make recommendations for antimicrobial products on the basis of efficacy.Systematic Review Registration:https://atrium.lib.uoguelph.ca/xmlui/bitstream/handle/10214/16236/Protocol_NMA_efficacy_dryoff_antibiotics_cure_IMI.pdf?sequence=3&isAllowed=y.
Highlights
Intramammary infections (IMI) that are left untreated during the dry period can develop into clinical mastitis (CM) in the subsequent lactation (Pantoja et al, 2009; Bhutto et al, 2011), which affects production and milk quality
Incidence of CM in the first 30 days in milk (DIM) in cows with an existing IMI was reported in six trials, and a metric for total antimicrobial use in the first 30 DIM in cows with an existing IMI was reported in one trial
Antimicrobials most often reported in the trials evaluating the treatment of existing IMI during the dry period were cloxacillin, penicillin-aminoglycosides, and cefapyrin products
Summary
Intramammary infections (IMI) that are left untreated during the dry period can develop into clinical mastitis (CM) in the subsequent lactation (Pantoja et al, 2009; Bhutto et al, 2011), which affects production and milk quality. The importance of curing and preventing IMI during the dry period has led to the development of indications, such as the Pan-European agreement on dry cow therapy (2017), which states that only animals likely to be infected should receive dry cow antimicrobial therapy, herds at high-risk for infections should be considered for the treatment with antimicrobials in addition to internal teat sealant products (Bradley et al, 2018). The evaluation of comparative efficacies of dry cow antimicrobial therapy options is important when selecting an antibiotic. The addition of a network meta-analysis allows the comparison of all dry cow antimicrobial products, which compares the products beyond the traditional pairwise metaanalysis of two interventions (Li et al, 2011). When enough evidence is available, network metaanalyses provide a rigorous synthesis of all available treatments to aid in clinical decision-making
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