As you all know my gray mare (who is 20 y/o ) had a foal May 1st. No trouble or any type of complications at all. Howdy is getting huge and doing well but my mare "Gray" is not coming back into heat. She showed no signs of foal heat or any other heat since foaling. I have chosen a very handsome, well bred dun stallion to breed her to this year and took her to the breeders and the vet administered a 2cc dose of estrumate to induce her heat cycle. Two other mares (one 22y/o one 8y/o) both got the same shot on the same day. That was last tuesday the 21st. Both the other mares have come into heat and been covered by the stallion. My mare is still not showing signs of heat and pins her ears when the stallion enters the room and kicks at him when he gets near her. She ran with the stallion at her previous home and only had foals every other year. I have called two seperate vets and both agreed that she should be given another dose of the estrumate and watched for another 4-5 days and if she doesn't show heat then she should be given an ultrasound to determine why she isn't cycling. Personally I feel comfortable leaving her open for a year if she isn't going to breed. I am concerned about messing with her hormones and cycles and what long term effects it may have especially with her age. She is in good flesh if not slightly chunky and passed her "manual" internal examination with flying colors before the first shot was administered. So my questions are this:

with her age and history of only producing foals every other year would YOU give her another shot if she were your mare?

is there such a thing as a mare who won't cycle if she has a foal on her?

what if any are the possible long term effects on the breedability of an older mare if you: A. force the heat cycle or B. leave her open for a year.
Here is a picture of the mare Gray

and a picture of her with her foal this year
