Mastitis is the most common disease and the leading cause for antibiotic use on dairy farms. Due to consumer demand, antibiotic use is becoming more scrutinized in animal agriculture. This year at the National Mastitis Council meeting, Dr. Pamela Ruegg from the University of Wisconsin – Madison discussed how treatment practices could lower antibiotic use on farms and save money. Ruegg listed five steps and considerations for making optimum mastitis treatment decisions.

1. Detection

The first step is detection. What is being detected is not the infection, but the cow’s immune response to the infection. If any of the common symptoms of mastitis are detected, milk samples should be collected for culturing and the cow separated to a hospital pen for further observation before a treatment is given.

2. Determine severity

The second step is to determine the severity of the mastitis case based on immune response. Ruegg detailed a severity scale from 0 to 3. Having a high SCC would relate to a score of 0. A score of 1 would be abnormal-appearing milk; abnormal milk and an abnormal-appearing udder would be a score of 2. During a severe case, score of 3, the milk and the cow appear abnormal, while the udder may or may not have an abnormal appearance.

3. Take action

After detection and determining the severity of the mastitis case, an initial action needs to be taken. In a severe case, symptomatic treatment should begin immediately. For non-severe cases, the cow’s history should be considered before a treatment decision is made. High-priority treatment options for cows with a severe case of mastitis are oral and hypertonic fluids along with nonsteroidal anti-inflammatories. Injectable antibiotics are important to prevent bacteria from spreading into the bloodstream. Intramammary antibiotics are considered a low priority for a severe mastitis case.

4. Determine antibiotic usage

The fourth step is to determine whether antibiotics will aid the immune system in curing severe or mild mastitis cases. To help determine whether or not the cow will benefit from antibiotics, her history needs to be reviewed. Variables to be considered include the cow’s age and stage of lactation, along with her history of previous mastitis cases, both clinical and subclinical, and the possibility of other existing diseases. Antibiotic therapy may not be beneficial if the infected cow has had a previous infection of a recurring pathogen, repeated treatments for clinical mastitis, a history of chronically high SCC or if the cow is infected with a concurrent disease.

5. Decide on the best treatment

The final step is to determine the best treatment option for the given case of mastitis. For those cases that do not require lactating cow antibiotics, cow history needs to be examined in order to make a logical treatment decision. Watchful waiting may be the best treatment option in most cases and needs to be considered when antibiotic therapy will not be beneficial. In a watchful waiting case, continuous monitoring should occur until inflammatory symptoms subside. Anti-inflammatories may aid in pain management.

An additional treatment option is dry cow therapy. Early dry-off is a consideration for high-value cows with a chronic mastitis case. At times, mastitis treatment is not economically viable, based on cow history, and the best option is culling from the herd. Only when culling is not possible due to the economic value of the cow, should she be separated from the rest of the herd and milked last to protect others from infection.

When antibiotic therapy is justified, many variables need to be taken into consideration to successfully aid the immune system against a mastitis case. The first is the invading pathogen. Culturing mastitis cases is important to determine optimal treatment options. Bacteria types affect the mammary gland in different ways. Staphylococcus aureus and klebsiella are two common mastitis pathogens that invade the udder tissue. Because of this, they are harder to cure. Bacteria that infect the mucosal surface, such as E. coli and CNS, are easier to cure, and extended therapy is often unnecessary.

Producers can either treat mastitis cases right away or wait until they receive culture results. Treatment that begins right away should be of short duration and reevaluated to accommodate culture results. If culturing is not a standard protocol, a short duration antibiotic therapy is recommended. Cow data and history of infection should determine whether long duration treatment is needed. More often than not, long duration treatment is not beneficial.

Mastitis is one of the most costly diseases in the dairy industry and the leading cause for antibiotic use. Dairy producers can save money and lower antibiotic use by becoming more selective about which mastitis cases are treated. Three things need to be considered to make more effective treatment decisions: the bug, the cow and the drug.

Knowing the infecting pathogen can result in better treatment decisions because pathogens have different effects on the mammary gland and respond differently to treatment. Depending on cow data and historical mastitis infection status, antibiotic therapy may not be successful or economical. Finally, the drugs and treatment regimen need to be considered. Severe cases should be treated right away to keep the bacteria from spreading into the bloodstream; with mild cases, it is often better to wait and watch.  PD

Derek Nolan is a graduate research assistant at the University of Kentucky.

Dr. Jeffrey Bewley is a dairy extension specialist at the University of Kentucky.