Expert opinion on livestock antimicrobial usage indications and patterns in Denmark, Portugal and Switzerland.

We aimed at describing antimicrobial usage patterns throughout livestock production cycles, and comparing them across three countries from Northern, Central and Southern Europe. Given the difficulties to collect such detailed usage data, an expert opinion was deemed the most appropriate study design. This study provides new insights into the time periods and indications for which specific antimicrobial substances are used in different livestock sectors. Veterinary experts (n=67) from different livestock sectors (broilers, pigs, dairy cattle and veal/fattening calves) and countries (Denmark, Portugal and Switzerland) replied to a questionnaire focusing on the time periods in the production cycle when antimicrobial substances were administered, and the respective indications for treatment. Our results showed that for several antimicrobials, between-country and within-country variations exist regarding the temporal distributions of treatments and indications for use. These differences were also true for several critically important antimicrobials, which is a matter of concern. Furthermore, differences between countries were also evident regarding the antimicrobial substances licensed. Based on our results, it is recommended to establish and promote treatment guidelines, invest in the prevention of diseases during critical moments of the production cycle and target undifferentiated use of antimicrobials. Moreover, discrepancies between countries should be further investigated to better understand the factors underlying the identified patterns and to distinguish prudent from non-prudent use. The results can inform decision-making with the aim to foster antimicrobial prudent use in the veterinary setting and, therefore, protect public health from the threat of antimicrobial resistance.