by Katie Navarra

Mastitis changes milk quality, but it is not always caused by the same bugs. Treatment and management decisions should reflect these differences. Most farms have zero tolerance for contagious bugs. Some pathogens like mycoplasma don’t respond to antibiotics, leaving farms no treatment options. This is one reason many farms cull cows with contagious mastitis.

In a webinar hosted by Cornell Pro-Dairy, veterinary epidemiologist Paula Ospina, DVM, MPH, Ph.D., shared best practices for the treatment and management based on mastitis type.

“Most of the antibiotic treatment options on the market have the same mechanism of action; therefore, which one you pick comes down mostly to the label instructions and what your farm can do,” said the milk quality and dairy training consultant. “For example, one is labelled for twice a day treatment and most of the others are once a day. We recommend that whatever tube you chose, pick the one that you can reliably follow the label.”

The cost of mastitis

Mastitis is the number one reason farms use antibiotics. All cows, even dry cows, are at risk for developing mastitis. Limiting cases of mastitis helps reduce the economic impact of the disease. A mild case could cost as little as the treatment and discarded milk or as much as losing a cow and her total milk production. In another webinar, Ospina said a general figure is $444 per case, based on a study that looked at the cost of mastitis in the first 30 days, which is when a lot of mastitis cases happen.

“In these hard times, anything that negatively affects milk quality, such as an increase somatic cell count, will have an even greater effect on a farm’s bottom line,” she said.

There are also added labor costs associated with dealing with mastitis – the time it takes to administer antibiotics. Since most contagious mastitis is spread in the parlor from milker hands and machines, improving milking procedures, focusing on dip coverage, attaching a machine to a cow that’s ready to let milk down and improving unit alignment to decrease the risk of slipping are critical to keeping herd mastitis cases low, with an ideal rate of less than 2%.

Prevention: The best option

For pathogens normally found in the environment, keeping the cow’s environment as clean as possible, making sure pre-dip is applied well and focusing on teat end cleanliness is essential. Prevention strategies depend on healthy teat ends, as this is the cow’s first line of defense against mastitis pathogens getting into the udder.

“Regardless of environmental or contagious pathogen, good milking procedures and a clean environment will help decrease the risk of mastitis in any herd,” she said. “So, we always talk about attaching a machine to a clean, dry teat in a cow that’s ready to let milk down.”

Culturing and antibiotic selection

Culture-based treatments decrease the amount of antibiotics that are put into cows. Treating mastitis is imperative but rushing ahead before confirming culture results can lead to less effective treatment outcomes. It is okay to wait for the lab results to return, according to Ospina. It takes most bugs a minimum of 24 hours to grow so it takes a minimum of 24 hours for results, but the timing also depends on whether an off-site laboratory or on-farm culture is used.

Once the culture results arrive, choosing an antibiotic depends more on a farm’s ability to follow through with label instructions than the type of bacteria found. Most intra-mammary antibiotics currently available have similar modes of action.

Since approximately 30% of culture results show no growth, and about another 30% result in a gram negative or other pathogen where intra-mammary treatment is not recommended, Ospina likes to think of it as culture treatment protocol focused more on what not to treat. For example, you should not put antibiotic tubes in the udder for gram negatives like E. coli, Klebsiella spp., etc.

The immune response of the cow is great and these pathogens are quickly eliminated. Often by the time changes are seen in the milk, these pathogens are mostly dead. Some cows will develop systemic signs of disease such as fever, dehydration, etc. They may need medicine like fluids, anti-inflammatory medication and systemic antibiotics (injections of antibiotics), but they usually don’t need antibiotics in their udder, she said.

Even well-managed herds have some level of mastitis, which decreases milk quality and creates a loss in production and decreases the quality of milk products. Monitoring for mastitis, establishing good milking procedures, providing clean bedding and culling animals from the herd all contribute to keeping cases as low as possible.