Abstract The study aimed to assess the potential to reduce antibiotic usage during the dry period of dairy cows and the associated environmental impacts by simulating potential cephapirin (Cefa-Safe) application according to the recording season and udder health status of the dairy cow population in Croatia. Official milk recording data from the Croatian Agency for Agriculture and Food (HAPIH) collected between 2013 and 2022 were used for the analysis. Based on these data, cows were classified according to udder health status: healthy (400000 cells/mL). Using these proportions, the total amount of cephapirin, its economic value, and potential environmental emission under the standard blanket dry cow therapy (BDCT) scenario were simulated. The analysis was conducted by season (spring, summer, autumn, winter). The highest estimated antibiotic usage and emissions were observed during summer in Holstein cows and in spring in Simmental cows, whereas the lowest values were recorded in winter for both breeds. The calculated risk quotients (RQ = PEC/PNEC) exceeded the threshold value RQ > 1 in all seasons, indicating a persistent environmental risk. The economic estimations followed the same pattern, with the highest costs recorded during the warmer part of the year. The results confirm that seasonal variation affects udder health status and consequently the amount of antibiotics potentially required during the dry period. The proposed model enables a quantitative assessment of the potential for reducing antibiotic usage and provides a scientific basis for transitioning from standard to selective dry cow therapy (SDCT) within the framework of sustainable dairy production.
Ljubojević et al. (Sun,) studied this question.