The ClassyFarm system, developed by the Istituto Zooprofilattico Sperimentale della Lombardia e Dell'Emilia Romagna (IZSLER), is owned by the Italian Ministry of Health. It started as a sample/survey system for pigs in 2014 and later it was opened up to dairy (2016) and poultry farms (2018), trials on beef farms have been made as well. During such phase, for pig and dairy cattle, AMU data was collected retrospectively on a convenience sample of 250-450 farms. For broilers and turkeys, data on 2015-2018 AMU has been collected for more than 80% of Italian poultry production. During 2019 the Italian electronic prescription system became fully operational, AMU data collected with such system is sent to the ClassyFarm database for further processing. Since tracking of AMU at age group-level is still being perfected, an additional indicator has been developed (DDDAit/biomass) that compares consumptions to the entire biomass of animals reared on a farm. The DDDAit/biomass indicator covers almost entirely the Italian production of pigs, dairy cattle, turkeys and broilers.

Animal subcategories: For AMU at age-group level, the distinguished weight categories in pigs are sows/boars, finishers, weaners and sucklers; in dairy cattle cows, heifers and calves are distinguished and in poultry broilers, turkeys and laying hens. For DDDAit/biomass, the AMU denominator is calculated by summing all the weights of the age groups present in a herd.

Input: For AMU at age-group level, data come from the Italian electronic prescription system (numerator) and the Italian Veterinary Database (denominator) or, when such data are incomplete, it can also be submitted by the IZLER staff, with assistance of vets, farmers or supply chain and company managers. For DDDAit/biomass, all the data came from the Italian electronic prescription system and the Italian Veterinary Database.

For AMU at age-group level, the dose-based unit of measurement DDDAit is used to calculate the number DDDAit per animal per period (which can be a semester or a year = the time-frame). Each active ingredient is considered as a single treatment, whether it is part of a combination product or not, with the exception of intramammary and intrauterine antimicrobials. The main indicator is DDDAit per animal per year; other indicators, such as AMU per semester may be provided as additional information. For finishers and the cattle subcategories, weights at treatment are standard estimations set on national level. For the other weight categories, EMA[1] weights are used. For DDDAit/biomass, a similar analysis is performed but without tracking AMU, within the same farm, broken down by age group

A farm’s AMU is compared to the median of all farms either at age group-level or at herd-level, depending on the indicator, and is also classified according to its quartile. Furthermore, other comparisons are available such as with medians at different geographical levels (i.e.; national, regional, metropolitan area) or at user level (i.e.; the median of all the farms a user is authorised to view). Usage of quinolones, 3^rd and 4^th generation cephalosporins and colistin are highlighted in red, macrolides in orange. AMU at age-group level was developed for antimicrobial stewardship while DDDAit/biomass is used to guide the selection of farms for pharmacosurveillance purposes. The 2020 was the first year fully covered by the Italian electronic prescription system, data and methodologies are currently under review and shall be refined in the next few years.

Farmers, vets and farmer groups/associations receive written reports and an oral presentation. Farm reports, which summarise up to three years of AMU, can be downloaded from interactive dashboards available for authorised users (veterinarians, public health managers, etc.). The first national report on AMU is currently under development.