Antimicrobial use in sows in Finland and its association with herd characteristics

Antimicrobial use (AMU) in food-producing animals affects development of antimicrobial resistance. Previous studies have shown that AMU for pigs varies considerably between herds and countries. Finland has relatively low AMU in pigs, although pigs are the main species treated with antimicrobials. In Finland, the use of medicines for pigs is recorded in the national web-based herd health and welfare register Sikava. We aimed to qualitatively and quantitatively describe AMU in Finnish sows using anonymous herd health data and to identify indications for antimicrobial treatment, antimicrobial agents used for each indication, and farm-level risk factors associated with AMU. Forty-eight randomly selected herds with more than 100 sows were selected from the herd register of 905 herds. The register data included AMU in sows, biosecurity evaluations, welfare index calculated by the Sikava system, and scores given by veterinarians during veterinary health care visits in 2022. Visiting veterinarians collect information on housing and environmental conditions, animal health, and welfare using a standardized protocol and record their findings electronically in the herd health register. Farmers record AMU in sows electronically in the register. Data for this study included the product name, active substance, treatment indication, duration of therapy, number of sows treated, and dosage. AMU in sows was quantified at the herd level as milligrams of antimicrobials administered per population-corrected unit (mg/PCU). Additionally, potential farm-level risk factors were identified. The median total AMU for the sows was 21.9 mg/PCU (range: 0.3-178.5). The most used antimicrobial was penicillin, and sows were most commonly treated parenterally for locomotory (34% of the treatments), udder (20%), reproductive (12%), and skin (11%) disorders. AMU was higher in large herds than in smaller ones. Piglet producers used more antimicrobials than farrow-to-finish herds, and AMU increased with higher internal biosecurity scores. AMU in Finnish sows varied widely between herds. Injectable penicillin was the most commonly used antimicrobial, and sows were most frequently treated for locomotory, udder, and reproductive disorders. Large herds, piglet producers, and herds with higher internal biosecurity scores had the highest AMU.