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My mare is aggressive to my new gelding. How can I help them?

Updated on September 23rd, 2025

Pet's info: Farm Animal | Horse | Female | 4 years and 2 months old | 1000 lbs

I have a mare and just got a new gelding about 1 week ago. My mare has been very mean and aggressive to the gelding. She chases him around relentlessly and kicks/ bites him, guards the water, and won’t let him near the shelter. I knew there would be some fighting but it doesn’t seem to be settling down. Is there anything I can do to help her get along better with him.

2 Answers

Most Helpful Answer

Linda G, MS, DVM

Answered By Linda G, MS, DVM

Veterinarian

Published on August 8th, 2019

Hello. First, know that this is normal behavior. Mares especially can be aggressive to geldings & even other mares. It can take several days to up to 3 months for everyone to settle down.
If possible, the horses should be separated where they can see, smell & possibly touch each other, but can flee if the situation requires it.
If you can not place the horses in adjacent paddocks, they should have separate resources far enough apart so that no guarding occurs. 2 water sources & feeding far enough apart ( or confining the mare ) until all grain is consumed & for up to 20 minutes after is necessary. Once the gelding has finished & is grazing quietly, you can release the mare.
If any of the horses are wearing shoes, pulling them temporarily may prevent significant injury.
If the behavior does not seem to at least be calming down in another week or so, you may need to have your mare evaluated for an ovarian problem or even granulosa cell tumor. These can cause significant hormonal changes in mares resulting in almost stallion type behavior.
Have patience, a week is only a short time to try to buddy up two horses.
Good luck & thanks for using Petco Pet Education Center, formerly Petcoach.
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