Ever wonder if one mare’s pregnancy can trigger a false pregnancy in another? Dr. Tom Lenz, past president of the American Association of Equine Practitioners, weighs in on the subject.

Question:

I have a mare that is due at the end of this month and I also have another broodmare that is not in foal (or so I was told), who is producing milk and getting fatter.

Is it possible that the broodmare is producing milk based on the other horse’s due date? I checked with her previous owners and he said she lost her last foal, which would have been her fourth.

Is it possible that she is going through a false pregnancy?

Answer:

The first thing I would do would be to have your veterinarian pregnancy examine the mare that you suspect of false pregnancy to ensure that she is not pregnant.  I’ve seen many mares through the years that were believed open, but were actually pregnant.

Some mares will develop a yellow, sticky material in their udder that we call “witch’s milk.” It’s not milk, but normal fluid.

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If you frequently check a mare for milk by squeezing the teat to see if she has milk, you can actually stimulate her to produce milk. Therefore, once your veterinarian has determined the mare is not pregnant, I’d recommend not checking her often.

It is also possible the mare has an infection in her udder, known as mastitis, that your veterinarian can determine during an examination.

– Dr. Tom R. Lenz
Senior Director, Equine Veterinary Services
AQHA Corporate Partner Pfizer Animal Health