Which antimicrobials are used and dispensed most frequently as dry cow therapy tubes? An analysis of Defined Course Doses (DCDvet) based on veterinary treatment data.

Objectives The aim of the current study was to analyse which antimicrobial active ingredients were used most frequently by a convenience sample of Austrian farm veterinarians as dry cow therapy. Materials and Methods A total of seventeen veterinary practices treating over 6700 dairy cows provided antimicrobial use data for 250 dairy farms over a period of one calendar year. All antimicrobials administered by the veterinarians themselves and those dispensed to farmers were recorded. Individual animal IDs, diagnosis data, as well as the number and amount of drug used were provided to the authors electronically. Animal movement and production data were provided from the Cattle Database (RDV) of the Austrian Federation of Cattle Breeders. The analysis presented here includes only intramammary dry cow tubes. Antimicrobial metrics were calculated using the European Medicines Agency unit of veterinary Defined Course Doses (DCDvet), where 4 dry cow tubes are equal to 1 DCDvet. Using the mean calving interval for each dairy farm as well as the annual replacement rate, DCDvet values per cow and year were adjusted to account for these factors as follows: Correction factor=(Calving interval (d))/365 × 100/((100-replacement rate (%))) Results The median adjusted DCDvet/cow/year for the study farms was 0.611 (mean 0.551). Each veterinary practice enrolled different numbers of farms in the study. For this reason and to ensure participant anonymity, the data here refer to the proportions (in percent) of adjusted DCDvet/cow/year for antimicrobial dry cow therapy (DCT) used by each practice on the study farms. The only “Highest priority critically important antimicrobials” (HPCIA, as defined by the World Health Organization) licensed for use in Austria for DCT and identified in this analysis was the fourth-generation cephalosporin, cefquinome. Of 17 veterinary practices, 12 (70.6%) did not use HPCIAs for dry cow therapy. Of those practices which did use HPCIAs, the highest level of use for one practice was 46.4% cefquinome of all dry cow therapy administration and prescribing, as calculated as a proportion of total DCDvet/cow/year. This practice used cloxacillin (44.3%) and the first-generation cephalosporin, cephalonium (9.3%) for the remainder of their dry cow therapy. Of all 17 practices, the most commonly used antimicrobial active ingredients for dry cow therapy were cloxacillin and ampicillin & cloxacillin combinations. Conclusions Overall, the veterinarians included in this study were responsible in their use of antimicrobials for dry cow therapy with the vast majority using non-HPCIA active ingredients. However, veterinarians in practice need to be made aware of their options with respect to prudent use and antimicrobial stewardship. The use of antimicrobial classes of critical importance to human medicine should be restricted to specific cases where alternative less critical classes of antimicrobials have been proven not to be effective through bacteriological culture and sensitivity testing.