Cushing’s Disease or Syndrome is caused by a benign tumor on the pituitary gland. It can be found in both sexes, and according to one article I found is most common is Morgan’s and ponies. There are groups that discuss Cushing’s with various vets that can help you with suggestions if your horse is struck with this disease. One of the members there told me that it was more common in Arabians, so I guess it depends on what you read and what their research has told them.
Some horses with the disease are also Insulin Resistant, and can develop severe Laminitis. The first tell tale signs are a long curly coat that does not shed out in the spring, a sway back, and a large hay belly. Their metabolism is affected as well as their ability to cycle properly, and thus it is difficult for a mare to settle. These are what you will find in any documentation you may read. What follows is from my own experience so while this has been true for our mares it is not necessarily true for all equines stricken with the disease.
Sarashea, our first mare was our first experience with Cushing’s. She was Rudy’s horse before she was ours, and he said since he first met her she had an excessive coat. She had, had one foal but hadn’t been bred since. She also had arthritis in her back end, which is not uncommon in Arabian/QH crosses. When I met her she was full of vim, and plenty of vigor. I wanted to breed her someday, but it was a few years later when we started breeding. Although a half-Arabian, she was a Serinosk daughter, a much desirable bloodline. I doubt that at this time there are any breeding daughters of Serinosk so I doubt I will ever have a horse that close.
Sara was always very healthy, and so we had no reason to think there was anything wrong, and less reason to have a vet check her out. We knew nothing about Cushing’s nor had we ever heard of it. It wasn’t until we were having Marina checked for AI that we were told that she was a Cushing’s mare. The vet also told us that it was doubtful that she could ever be bred. He didn’t say much else, and didn’t seem to be concerned about it so we weren’t either.
We moved from the coast to Auberry outside of Fresno, and the vet there asked about Sara being a Cushing’s mare, we said yes she was. Like I said we were terribly ignorant at this point. She did tell us that later she would probably founder, and end up with Laminitis. The only thing we could do was to give her Bute when she foundered, and watch her. By this time we were not riding her much anymore because it seemed to be a bit much for her no matter that she loved it, and had an uneven gate because of her arthritis. We did however let her out with the girls so she could run in the pasture. No exercise is never a good thing, that much we did know. She foundered as predicted, and we got her through it only to have her founder again. That’s when Rudy said enough was enough, and we put her down. He couldn’t stand to see her in such pain.
The first year after we moved to New Mexico none of our mares settled, but the next year the mares we bred settled except for Marina. We tried breeding her again, and again we had no luck even though she did not come back in season. We thought she had settled because her belly grew and she became less active. When her due date came and went we thought perhaps she thought she was pregnant because she was next to Sadie, and Sadie was definitely pregnant. That winter she started having problems with her feet, and her coat was way too long, that’s when we had Warren our vet, check her out. I started looking on the Internet for information, and I found a chat group just for Cushing’s horses. I learned a lot from them, but Marina only showed signs of a long coat, and lethargy. When the tests came back they showed that while she was not IR she did have Cushing’s. I had already started her on Chaste Berries, which has shown improvement in some horses, but when that didn’t seem to work we put her on Thyro-L as Warren suggested.
As you might guess Thyro-L is used for horses that have a Thyroid condition. It is also used on Cushing’s horses since the tumor affects the Pituitary gland’s ability to produce hormones. She did improve. Her lethargy was gone, her feet weren’t bothering her, and she began shedding out. She did not however start cycling. Even though people on the chat group were appalled that I would even consider breeding her, I was not about to not have a foal to replace her if we had to stop breeding her. She was only 15, and had a lot of babies still in her. I also spoke with a research veterinarian friend of mine, and she said as long as she is healthy, she could see no reason not to breed her. Warren seemed to think that it was all right, and since we think of him as all knowing (well not quite), I couldn’t accept never again. He then put her on Pergoloid a medication that was developed, and given to Parkinson’s patients. Why it works on Cushing’s I have no clue, but she came into season, shamelessly teased poor Ibn till he was crazy, and settled first time round.
It seemed after she took, she got a new lease on life, and was once again our Marina. She had a beautiful filly (as usual), and has continued to be healthy, and happy if a bit more spoiled. She has to have her Thyro-L every day, and since it’s a fine powder, of course I give it to her with pellets (Safe Performance), and she can’t get it fast enough. I continue to feed her supplements with low sugar even though she is not IR just because. Arabians have more than enough energy with out giving them more sugar or starch. We don’t need it, and neither do they. My veterinarian friend said that some studies show that some Cushing’s mares do better when kept pregnant. She also suggested that this might be because while pregnant, they do not have the hormonal fluxuations of having a regular cycle.
If you ever have a horse with Cushing’s, read all you can, and do what seems to work for your horse. Every horse is different, and they react differently to different diseases just like we do. Once you get your horse stabilized there is no reason not to breed them if they are healthy, and strong enough. Even now they are developing new medications to help your horse continue to live a long, and healthy life. Be proactive, if we had researched more maybe we could have bred Sara or at least given her a longer, and happier, pain free life.