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New mare bagging up, clear yellow fluid

Hi all,

Our new rising 4 year old mare arrived at our stable two weeks ago and I was surprised by the size of her teats. This is a just broken sporthorse, assumed to be maiden. Anyway, she bagged up yesterday.

We had our vet come out to examine her but were unable to do an internal exam (no breeding stocks on site, sharp young horse). She used the rectal ultrasound probe to scan externally along her abdomen and found no evidence of a placenta. However she expressed a clear, yellow serum-like liquid from her teats— no odor, slightly sticky. Our mare’s udder was not sensitive to the touch and did not feel as our vet would expect a mastitis case to present. Temp and respiratory rate were all in a normal range. She collected the fluid as well as a blood draw, so we should hopefully have an answer next week. But I am so curious… has anyone had a similar experience or any guesses what might be going on? :see_no_evil:

Phytoestrogens can make that happen, usually from
clover or soy.


Thank you for your response! Our grain does contain soy but we feed her quite a small amount… 2/3 scoop/day of a muesli type mix. That’s actually frightening if two weeks’ feed can do this to her. Finding soy-free where I live (outside US) is a challenge

It can be a combo factor of fluctuating hormones: changing seasons, new location, new feed, etc. Alfalfa can be another contributor.

I have a mare who has done it on and off her whole life despite never being bred. I also have a yearling who did it over the summer when the clover was at its peak.


That makes total sense. We just hit a heatwave here as well after a cool, rainy summer.

I will come back and update if the lab work shows anything different :slightly_smiling_face:

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