title: Effect of different scenarios for selective dry-cow therapy on udder health, antimicrobial usage, and economics.
abstract: The goal of dry-cow therapy (DCT) is to reduce the prevalence of intramammary infections (IMI) by eliminating existing IMI at drying off and preventing new IMI from occurring during the dry period. Due to public health concerns, however, preventive use of antimicrobials has become questionable. In this study, we evaluated the effects of 8 scenarios for selecting animals for DCT, taking into account variation in parity and cow-level somatic cell count (SCC) at drying off. The aim of this study was to evaluate udder health, antimicrobial usage, and economics at the herd level when using different scenarios for selecting cows for DCT. To enable calculation and comparison of the effects of different scenarios to select cows for DCT in an "average" herd, we created an example herd, with a virtual herd size of 100 dairy cows to be calving during a year. Udder health, antimicrobial usage, and economics were evaluated during the dry period and the first 100 d in lactation, the period during which the greatest effect of DCT is expected. This leads to an estimated 13,551 cow-days at risk during a year in a 100-cow dairy herd. In addition to a blanket DCT (BDCT) scenario, we developed 7 scenarios to select cows for DCT based on SCC. The scenarios covered a range of possible approaches to select low-SCC cows for DCT, all based on cow-level SCC thresholds on the last milk recording before drying off. The incidence rate of clinical mastitis in the example herd varied from 11.6 to 14.5 cases of clinical mastitis per 10,000 cow-days at risk in the different scenarios, and the prevalence of subclinical mastitis varied from 38.8% in scenario 1 (BDCT) to 48.3% in scenario 8. Total antimicrobial usage for DCT and clinical mastitis treatment varied over the scenarios from 1.27 (scenario 8) to 3.15 animal daily dosages (BDCT), leading to a maximum reduction in antimicrobial usage of 60% for scenario 8 compared with BDCT. The total costs for each of the scenarios showed little variation, varying from €4,893 for scenario 5 to €5,383 for scenario 8. The effect of selective DCT compared with BDCT on udder health, antimicrobial usage, and economics is influenced by the SCC criteria used to select cows for DCT. Scenario 2 resulted in the lowest increases in clinical and subclinical mastitis compared with BDCT. The greatest reduction in antimicrobial usage was achieved under scenario 8. From an economic perspective, lowest costs were achieved with scenario 5. Drying off dairy cows with antimicrobials has an effect on udder health, antimicrobial usage, and economics.
authors.affiliation: GD Animal Health, PO Box 9, 7400 AA Deventer, the Netherlands. Electronic address: c.scherpenzeel@gdanimalhealth.com.
authors.forename: C G M
authors.initials: CGM
authors.lastname: Scherpenzeel
authors.affiliation: GD Animal Health, PO Box 9, 7400 AA Deventer, the Netherlands.
authors.forename: I E M
authors.initials: IEM
authors.lastname: den Uijl
authors.affiliation: GD Animal Health, PO Box 9, 7400 AA Deventer, the Netherlands; Department of Farm Animal Health, Utrecht University, PO Box 80151, 3508 TD Utrecht, the Netherlands.
authors.forename: G
authors.initials: G
authors.lastname: van Schaik
authors.affiliation: GD Animal Health, PO Box 9, 7400 AA Deventer, the Netherlands.
authors.forename: R G M Olde
authors.initials: RGMO
authors.lastname: Riekerink
authors.affiliation: Department of Farm Animal Health, Utrecht University, PO Box 80151, 3508 TD Utrecht, the Netherlands; Chair Group Business Economics, Wageningen University, PO Box 8130, 6700 EW Wageningen, the Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Hogeveen
authors.affiliation: GD Animal Health, PO Box 9, 7400 AA Deventer, the Netherlands; Department of Farm Animal Health, Utrecht University, PO Box 80151, 3508 TD Utrecht, the Netherlands.
authors.forename: T J G M
authors.initials: TJGM
authors.lastname: Lam
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D000890:Anti-Infective Agents / Q000494:pharmacology; D002417:Cattle; D002452:Cell Count / Q000662:veterinary; D005260:Female; D007774:Lactation / Q000187:drug effects; D008321:Mammary Glands, Animal / Q000187:drug effects*; D008414:Mastitis, Bovine / Q000453:epidemiology*; D008892:Milk / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents
keywords: antimicrobial reduction; dry-cow therapy; economics; mastitis