Michigan State University Extension announced on May 4 that Dr. Pamela Ruegg, DVM, is summarizing her team’s research papers about mastitis treatment in a new video series available on her YouTube channel. The series focuses on the economic aspects of treating mild and moderate cases of mastitis during lactation, including costs related to milk discard, antibiotics use, and decisions about selective dry cow therapy.
The topic is important because mastitis remains a significant challenge for dairy farmers due to its impact on animal health and farm profitability. The research aims to help farmers make informed decisions that can reduce unnecessary costs while maintaining herd health.
A study led by Carolina Pinzon-Sanchez under Dr. Ruegg compared three strategies for treating clinical mastitis in early lactation: using on-farm culture before deciding to treat with antibiotics, starting antibiotics immediately but adjusting based on culture results, or treating without performing cultures. The researchers found that longer antibiotic treatments—five or eight days—consistently resulted in higher economic losses compared to shorter two-day treatments or no antibiotic use at all. According to Dr. Ruegg, “The economically optimal decision was to either treat with a two-day course of antibiotics, or to not treat with antibiotics at all.” She also said that while longer treatments slightly increase cure rates for some pathogens, this does not offset the greater financial loss from discarded milk.
Treatment recommendations depend largely on the type of pathogen causing the infection. Gram-positive bacteria such as Staphylococcus aureus typically respond well to short antibiotic courses and are sometimes contagious within herds through milking equipment. In contrast, infections caused by Gram-negative bacteria like E.Coli usually do not benefit from antibiotic treatment because they are less likely to spread between cows and have lower cure rates with medication.
Dr. Ruegg said that if an on-farm culture shows no bacterial growth after incubation—a result seen in 35% of samples—antibiotic treatment is unnecessary as the cow’s immune system has likely resolved the infection already: “Treating mild or moderate mastitis without determining the pathogen causing the infection is deciding on a treatment with incomplete information.” She recommended avoiding antibiotics when cultures are not performed since most cases would not benefit from them.
Accurate diagnosis using culture plates helps guide effective mastitis management strategies and prevents avoidable expenses for dairy operations.
The College of Agriculture and Natural Resources at Michigan State University addresses challenges in food, health, and environment through education and outreach according to its official website. It extends its presence across Michigan via research centers and extension services according to its official website, collaborates through 15 major research centers while engaging participants via MSU Extension according to its official website, reported an enrollment of 3,735 students along with more than 340 scientists involved in research during fall 2021 according to its official website, and focuses efforts toward fostering a healthy world through student preparation as well as sustainable agriculture practices according to its official website.
