Antimicrobial drug use on Austrian dairy farms with special consideration of the use of "highest priority critically important antimicrobials".

The use of antibiotics in livestock production is coming under growing criticism. Beside overall antimicrobial use, specific substances listed by the WHO as "highest priority critically important antimicrobials" (HPCIAs)--these include fluoroquinolones, macrolides, 3rd and 4th generation cephalosporins, as well as glycopeptides--have been placed under specific restrictions and should only be applied in particular cases according to strict indication criteria. In this study, the consumption of antimicrobial substances on Austrian dairy farms was evaluated quantitatively. The data covered 8,027 prescription records on the use of antibiotics on 465 dairy farms. Eleven veterinary practices provided data from between four to 27 months during the period from 2008 to 2010 and the total consumption of antimicrobials was estimated. The amount of active substance(s) in grams used per livestock unit (g/LU) per year and the number of product-related daily doses used per livestock unit (n PrDD(LU)/LU) per year were determined as units of measurement. These parameters were estimated by applying Monte Carlo simulation techniques, respecting variances in annual working days of the veterinary practices as well as variances in the proportion of non-treated populations. Total antimicrobial consumption in the population-at-risk was determined to be 2.59 g/LU and 1.30 PrDD(LU)/LU per year. HPCIAs were used at a proportion of 24.6% (0.31 PrDD(LU)/LU) of the total consumption of antimicrobials for systemic and intramammary use. Of these, 3rd and 4th generation cephalosporins were most frequently administered, particularly for the treatment of mastitis and foot diseases. The total consumption of antimicrobials in Austrian dairy cattle production is negligible compared to their use in pig and poultry production systems. However, the use of HPCIAs, especially 3rd and 4th generation cephalosporins, should be minimised further.