MSU Extension

While research has shown that selective dry cow treatment may be just as effective as blanket dry cow treatment of every cow and every quarter, differences in herds and management must be a consideration in the likelihood of success. What are the characteristics that make a herd a good candidate for selective antimicrobial treatment at dry-off?

In the studies cited in the second article of this series, “Selective dry cow treatment research results”, there were significant herd differences in the impact of selective dry cow treatment. In this final article from Michigan State University Extension, we will try to put the findings from research studies on selective dry cow treatment into practical guidelines.

At the onset, we recommend that this be a conversation that you have with your herd veterinarian. Overall health management and monitoring of performance needs to be a team effort with your veterinarian. Consider these criteria for herds with the potential to reduce or eliminate dry cow treatment.

1. Herds with well-controlled mastitis as indicated by SCC - Antimicrobial treatment is a tool for control of mastitis. It should never be used as a substitute for good management nor as the primary tool for mastitis control. In order to be successful without the full use of that tool, other control measures should be strengthened. For this reason, we would not recommend that herds with average SCC > 150,000 consider selective dry cow treatment.
2. Herds that have eliminated contagious mastitis organisms - Contagious organisms can be effectively controlled with dry cow antimicrobial treatment. Therefore, we would recommend that herds considering reduced or eliminated dry cow treatment have well-characterized mastitis pathogens through culture. You can’t know whether you have eliminated contagious organisms unless you are culturing milk.
3. Closed herds – Well-characterized mastitis within a herd means that we are not continually introducing unknowns.
4. Herds that eliminate re-infected cows - Re-infection of the same quarter is a reason for culling rather than a reason for re-treating. The probability of success with re-treatment is low and these animals should be culled rather than sent through a dry period without treatment.
5. Herds that set a criteria for dry cow treatment and apply it consistently - Select your criteria in consultation with your veterinarian and stick to it until you have sufficient results to judge whether to change the criteria.
6. Herds that reduce the risk of dry period infections - Over half of the clinical coliform mastitis cases in early lactation have been shown to originate during the dry period. Reduce the exposure of the teat end to bacteria by providing a clean, dry environment for cows, not over-crowding the dry cow pens, and using good infusion technique for dry treatment and sealant.
7. Herds that monitor outcomes - The effects of a change from blanket dry cow treatment to selective treatment may not be apparent for some time and must be monitored over the long term. Monitor the rate of new infections, SCC and repeat infections to make sure that mastitis control is not suffering. Knowing pre-existing clinical mastitis incidence and new infection rate (based on individual cow SCC) before starting on a selective dry therapy path is critical to monitor any changes in dry cow therapy programs.

Effective mastitis control is critical for the production of high quality milk by healthy cows. Yet, this alone may not be enough for consumers who also want to know about farm antimicrobial use and how that may impact them.

For managers with the ability and time to monitor and bacteriology of the herd, selective dry cow antimicrobial therapy may be successfully implemented. The advantages are numerous including moving towards reducing overall antimicrobial usage in food producing animals which is important for maintaining consumer confidence in the food we produce.

Additional articles in this series:

• Is it time to reconsider blanket dry cow treatment programs?
• Selective dry cow treatment research results