What you see. The starting point for addressing any equine health related issue is your observation.


Swelling of Udder or Teats


Horse owners and caretakers sometimes report mysterious and unexpected swelling of the udder. Obviously, the first question is the mare's reproductive or lactation status.

The mare could be pregnant. Healthy pregnant mares begin to develop an udder at about 6 weeks prior to their due date. Udder swelling prior to this time could indicate a problem with the pregnancy and impending abortion. It would need to be investigated.

Excessive swelling of an udder in a lactating mare, indicating that the foal is not nursing, there is udder infection or the udder has sustained trauma.

For mares that are not pregnant and are not lactating, swelling of this area could be caused by inappropriate lactation. Some mares lactate despite not being pregnant and not nursing a foal. Generally, this type of lactation ("witches milk") is not a great concern. Swelling from this is usually soft and fluid feeling and often limited to the teat itself. When milked, secretion is present.

However, other causes of swelling of the udder in a non-pregnant, non-lactating mare include mastitis, trauma to the udder, tumors, or swelling spreading from a problem involving a nearby area (like the belly or groin).

  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • If you are concerned about the pregnancy or the mare and want an evaluation.
  • Code Yellow

    Contact Your Vet at Your Convenience for an Appointment
    • If the swelling is mild or moderate, and not increasing rapidly.

your role


What To Do

Assess the mare's general health using the Whole Horse Exam (WHE). Try to strip some milk from the udder. Is there a secretion? Is the mare well otherwise? Contact your vet with your findings and concerns.

your vet's role

Your vet considers the mare's reproductive and general health status and determines a diagnosis for the swelling. This may analysis of any secretions in the udder as well as careful assessment of the area.
Questions Your Vet Might Ask:
  • Do you notice that the mare is producing milk?
  • To your knowledge, is the mare pregnant?
  • What are the results of the Whole Horse Exam (WHE)?
  • Can you squeeze any secretion out of the teats?
  • What does the secretion from the teats look like?
  • What were the mare's breeding dates?
  • Do you notice swelling of the underbelly or groin?
  • What does the swelling feel like?

Treatments Your Vet May Recommend

A way to resolve the condition or diagnosis. Resolving the underlying cause or treating the signs of disease (symptomatic treatment)

Very Common
more treatments

further reading & resources

Author: Doug Thal DVM Dipl. ABVP