Profile of etiologic agents causing clinical mastitis and antimicrobial use in dairy herds

Abstract

This study aims to determine the etiologic profile and antimicrobial susceptibility of clinical mastitis pathogens, and to describe the qualitative and quantitative aspects associated with antimicrobial drug usage for treatment of mastitis in dairy herds. The study will be performed by development of three experiments: Experiment 1 - Determination of etiologic profile of clinical mastitis in dairy herds; Experiment 2 - Quantification of antimicrobial drug usage for treatment of mastitis; and Experiment 3 - Economic approach and evaluation of risk factors related to a program of on farm microbiological culture. For experiments 1 and 2, milk samples and data related with antimicrobial use will be collected from 15 dairy herds during 12 months. Data will be collected to determine the prevalence, incidence, clinical mastitis causative pathogens, score of severity, treatment protocols and antimicrobial drugs used, estimation of milk disposal and rates of recurrence and new intramammary infections. Isolates diagnosed as Staphylococcus aureus, Streptococcus agalactiae, Streptococcus uberis and Escherichia coli will be analyzed for minimum inhibitory concentration and genotypically analysed by PCR-random amplification of polymorphic DNA (RAPD-PCR). The quantification of antimicrobial will be developed by estimating the defined daily dose of antimicrobial drugs used for treatment of mastitis and dry cow therapy. In experiment 3, lactating cows from three dairy herds will be randomly assigned into two treatment groups to determine risk factors related to on farm microbiological culture program, and for economic approach of this program as compared with immediate treatment of cows with clinical mastitis.