I have a 20-year-old paso fino mare with multiple cysts. She was bred by AI to a very fertile stallion, kept on Regumate 120 days and gave me a gorgeous filly in April after a by-the-book pregnancy and delivery. When I had the vet out to re-breed to same stallion, he found multiple HUGE cysts. He "popped" several cysts and after a few weeks we bred her again. The timing of the breeding was perfect. She didn't settle. The vet thinks the cysts may have interferred with uterine recognition of the pregnancy. He says that cysts tend to get very large after pregnancy but will shrink with time. Is this true? What causes uterine cysts in the mare anyway?
Anonymous Posted From: 18.104.22.168
Posted on Friday, August 01, 2003 - 08:06 pm:
I was told by a vet that horses don't (rarely) develop uterine cysts
Jos Posted From: 22.214.171.124
Posted on Saturday, August 02, 2003 - 11:35 am:
Endometrial (the lining of the uterus) cysts are very common in older mares, so I am afraid if that is what your vet told you, they are not "up to scratch" on equine reproduction.
I purchased a 17 yr. old mare in foal last December. In late April she delivered a strong healthy foal with no foaling complications, (this was her 5th foal in a row). We were preparing to breed on the foal heat, however had some uterine fluid clearance issues even though we had already given oxytocin for a couple days following delivery. We then did another oxytocin regime to clear the extra fluid, short cycled the mare, and ai'd with shipped semen in late May. This mare also had a uterine cyst which seemed to be increasing in size. The mare conceived and the embryo came down and seemed to bump right against this cyst and attach next to it. This made things a little complicated in reading the next couple of ultrasounds, however we did have a heart beat. We then ultrasounded the mare in late July to discover she was no longer pregnant. At this point of course it was to late to do any further breeding for that season. After reading a post which I believe was by Jos that indicated some cysts will diminish as the breeding season goes away, and the secret with these mares can be to try and get them in foal early the next season I decided it was the route I would take. I waited until Oct. and had my vet ultrasound the mare and sure enough the cyst had significantly diminished in size. I have put this mare under lights as of early Nov. Please note we are located in eastern Washington and have true winters with plenty of snow and low temperatures. Since we generally do our breeding mid April through mid May I have never had to concern myself with early conception. I would like to know how early and what protocal Jos would recommend to get this mare in foal to allow the pregnancy to attach without this cyst having a chance to enlarge again and get in the way. I am working under the assumption that these cysts enlarge due to hormonal influence during breedable heat cycles.
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