Over the past years, there has been a trend toward not treating clinical mastitis cases in some herds. In some instances, this philosophy has evolved from a fear of contaminating a tank of milk with antibiotics. In other cases, it has been a result of poor response to treatment. 

It is important to evaluate both current research and on-farm data to make an educated decision on when to treat clinical mastitis.

If you review the literature, it is generally accepted that Staphylococcus (Staph.) and coliform (E. coli and Klebsiella) infections do not respond well to intramammary therapy during lactation. On the other hand, cure rates often improve when Streptococcus (Strep.) mastitis cases are treated with approved intramammary antibiotics. So, how should we treat mastitis cases?

Proper identification needed

Treatment based on identification of the mastitis-causing bacteria is our best option in terms of cow health and economics. These types of culture-based treatment protocols have produced excellent results. 

The basic procedure as is follows:

  • A milk sample is taken for culture when mastitis is diagnosed.
  • If the cow is not sick or off feed, then no treatment is started. These cows are identified and the milk from that cow (or from that quarter) is not put in the tank. Because the cow is not treated yet, the milk from the unaffected quarters is saleable. Some farms use quarter-milk isolators to keep the affected quarter out of the tank.
  • The sample is cultured either on-farm, or dropped off to your veterinary clinic or milk-quality lab. On-farm culturing provides results in about 18 hours. Results from the clinic or lab are usually available in 24 to 48 hours.

If the mastitis case is caused by Strep., then treatment with an approved intramammary antibiotic is instituted. 

If the mastitis case is caused by either Staph. or a coliform, then no intramammary treatment is used. The milk from the affected quarter is isolated until the clinical mastitis has resolved.

Reduce lost profits

This treatment method reduces drug cost associated with intramammary antibiotics. And it reduces the amount of waste milk discarded for antibiotic withholding times during and after treatment. Because the cure rates for Staph. and coliform infections are similar whether antibiotics are used or not, the time to clinical cure is similar. 

Herds that have used this type of treatment protocol for many years have not seen any significant increase in the number of clinical mastitis cases nor an elevation in herd bulk tank somatic cell counts. To the contrary, these herds have maintained excellent SCC and overall udder health while reducing milk discard and drug costs.

With the approval of intramammary antibiotics with a label for extended treatment (up to eight days), we have been given options to become more aggressive with the treatment of mastitis cases that have a greater likelihood of cure. 

In certain early cases of Staph. aureus mastitis, we may recommend treatment to prevent the infection from becoming chronic or spreading to another cow. If this infection is already chronic, then treatment is not warranted during lactation but should be considered during the dry period.

On-farm milk culturing is a straightforward procedure that can be implemented on any dairy farm.  Implementing successful mastitis-treatment protocols involves a group effort, including the recommendations of your herd veterinarian on the proper use of approved intramammary antibiotics.

Mark J. Thomas is a veterinarian and owner of Countryside Veterinary Clinic, LLP in Lowville, N.Y.