MSU researchers reviewed non-severe cases of clinical mastitis for approximately 50,000 cows on 37 commercial dairy farms in Wisconsin. Overall, the findings suggest that for routine treatments, following the minimum labelled duration for mastitis treatment drugs is critical to maintaining animal and human health.  

The study indicates the need to reexamine the duration of treatment for mastitis in dairy cows. Unless improved clinical outcomes can be justified, cows should be treated using the minimum duration listed on product labels, and for shorter durations. This would benefit human health benefit by releasing fewer antimicrobials into ecosystems, therefore reducing the risk of antimicrobial resistance (AMR).

There are five existing products labeled to treat clinical mastitis in the U.S. The U.S. Food and Drug Administration (FDA) -approved labeled duration of treatment with the five drugs ranges from one day to up to eight days. People typically treat for five days because that is the average time the milk remains visually abnormal, and dairy farmers feel like they should treat until it looks like the mastitis is cured. However, previous MSU studies have shown that abnormal milk appearance is from inflammation, and it is not predictive of outcomes like the presence of bacteria or infection recurrence.