Dr. Heather Mack talks thyroid problems, healing and respiratory issues with EW readers to help shed some light on some common equine concerns.

Q: My young mare is in full work and only receives hay and a basic vitamin/mineral supplement. The grass in the pasture she is in stays cropped down – there is really only enough there to keep the horses occupied. Despite all this, she continues to put on weight, and is now developing a fairly cresty neck. I am concerned about the potential problems this could cause (i.e. founder). Someone mentioned she could have a thyroid issue – can horses develop thyroid problems? What causes it and what can I do about it?

A: Yes, horses do develop thyroid problems, though no one is certain why. Normally, bloodwork is done to check for levels of T3 and T4. I feel a TSH test is more conclusive. TSH or thyroid stimulating hormone occurs naturally in the horse’s pituitary gland, and stimulates the thyroid to produce thyroid hormone. Your veterinarian can give the horse TSH, then measure the amount of thyroid hormone produced; this gives a more accurate measurement of the level at which the thyroid gland is functioning.

Many people will just give a horse like yours Thyro-L or other feed additives containing thyroid hormone. Sometimes this works just fine. From a holistic standpoint, however, if the thyroid gland is already a bit sluggish, and we give the horse synthetic thyroid hormone, her thyroid may just stop working altogether.

I would prefer to stimulate your mare’s metabolism and endocrine system. First of all, more exercise would be my best advice; also, as little sugar as possible because she sounds to me like an insulin resistant horse. This is also known as Equine Metabolic Syndrome. Your mare fits the profile: obesity, regional adiposity or changes in fat deposition, and cresty neck. You can soak her hay to get the sugars out before you feed it to her. Conventional veterinarians put these horses on sometimes rather high doses of synthetic thyroid hormones as a feed additive.

I start with a slow but progressive exercise program, a diet with the least possible sugar, acupuncture or acupressure, Cymatherapy (, and essential oils to stimulate the endocrine system as well as #26 Thyroid and/or #28 Pituitary herbs from Silver Lining Herbs ( If this doesn’t work, I will go to the synthetic Thyro-L product. There is a good test available to measure the insulin/glucose levels in your horse’s blood. Perhaps you should start with this and the TSH tests to see what is really going on with your mare.

Q: What does it mean when someone says a horse is a “roarer”? Does it affect him performance wise? Is surgery the only option?

A: Horses with laryngeal hemiplegia are often called “roarers” because of a characteristic stridor or whistling noise they make, especially during exercise. It usually occurs on the left side of the horse and is due to paralysis of the left recurrent laryngeal nerve. This is a branch of the vagus nerve that runs along the jugular furrow; it innervates the arytenoid cartilage which normally opens and closes as the horse breathes. Since the paralysis is only on one side, air still can get in and out but there is less airspace, sometimes by 50%. So yes, it can definitely affect performance. I have seen it happen after IV injection mishaps where the medication got out of the vein. In Thoroughbred horses, some think it has something to do with the massive size of the heart muscle, and how that might affect the vagus nerve. There is also evidence that it could be hereditary.

If your horse does endurance or races or is expected to perform at high speeds, then you have to consider surgery. It is the only way to allow maximum athleticism in your horse. However, the problem is not always 100% fixed after surgery. In fact, one of my young Warmblood jumpers was done by one of our country’s top equine surgeons, and the operation failed, even with all my extra efforts for success. He had another equally famous surgeon do a second surgery and the ultimate outcome was adequate. The horse has had a successful show jumping career, but you can still hear him going around the ring. Not much different from where I started, and many thousands of dollars later.

If you are not expecting high levels of performance from your horse, I suggest you try to live with it, but understand the condition and know your horse will have limitations. Keeping him fit helps, and keeping his immune system strong is also highly recommended, whether you choose surgery or not.

Q: When my gelding gets a cut or scrape, it takes much longer than I am used to for it to heal, and it is quite some time before the hair grows back in the affected area. Why might this be?

A: Three factors come to mind when I hear about a slow healer. First of all, is there an environmental reason? Does he live under power lines or next to a freeway? Secondly,it could be genetic. Lastly, there could be a health issue. For instance, hypothyroid horses tend to heal slowly. Or he may have a mineral deficiency; there are areas of the country that are deficient in certain minerals. Nutritional imbalances such as a deficiency in vitamin C can cause a decrease in the synthesis of collagen. Zinc deficiency can also cause decreased collagen synthesis, decreased cell proliferation, and epithelialization.

I would start with a basic chemistry screen and check thyroid hormone levels for a quick overview of your horse’s health. I would also offer him the free choice mineral stress kit from Advanced Biological Concepts ( Circulation is critical to wound healing, so perhaps you can experiment with modalities such as laser therapy, infrared, or micro-current therapy the next time you have a wound to heal. I use all these with great success. I also love to use essential oils because they are so highly oxygenated and have such anti-infectious qualities. If you want to delve deeper into your horse’s nutritional and mineral status, you can have a hair analysis done.

Q: My 19-year-old gelding has been developing what appear to be fatty lumps/deposits on his back, in the area where the saddle goes. Why do these occur? Will they hurt him if I ride him and is there any way to get rid of them?

A: This question leaves too many unknowns for me to answer accurately. However, I can speculate and try to sort it out. If these are large fatty deposits, are they only under the saddle area or does he have what we veterinarians call regional adiposity elsewhere? If so, does he have changes in his hair coat, and a cresty neck? Does he seem to be drinking and urinating more frequently? If so, then I would be looking up more information on equine metabolic syndrome or insulin resistance. This condition can easily turn into Cushing’s disease, especially in older horses. You will need your vet to help you sort this out. In this case, it should not hurt him to be ridden; in fact, exercise is the best medicine as long as he is sound. Be sure you are using a saddle that is comfortable. I’m sure he will let you know if it is not.

If these are small fatty lumps that are only under the saddle, I’m thinking of furunculosis. This can be caused by bacterial or viral infections in the hair shaft. It may also be a condition known as “fistulous withers”, caused by the brucella abortis bacteria. It is highly contagious, and can be very difficult to get rid of. The least problematic possibility is that they are simply fatty tumors known as lipomas, or sebaceous cysts which usually don’t cause any trouble at all. The only way to be sure is have your veterinarian biopsy the lumps. I would not put the saddle on until your vet has done an exam.

Q: My mare is prone to mild respiratory issues (wheezing, coughing). I keep her outside 24/7 and am careful to keep her environment as dust free as possible. Are there any other ways I could support her respiratory system?

A: Yes. Pay more attention to what sets her off. Is it seasonal? If so, is it the weather or an allergy to pollens or local flora? Does it worsen with a new shipment of hay? Noticing these kinds of things will help you be more proactive in preventing respiratory episodes. Your veterinarian can do a simple blood allergy test to help identify allergens. If you have access to a holistic veterinarian who is competent in applied kinesiology or “muscle testing”, you can use it to check all her supplements and feeds to be sure she is not being constantly aggravated by something she regularly eats. She may only want meadow grass hay, for instance; timothy and alfalfa may affect her negatively.

Other things to try include acupressure on her lung points as well as her immune points. Find a veterinary acupuncturist to help you, even having it done quarterly can make a big difference. I show my clients points they can stimulate with acupressure, laser or even applications of essential oils. I do an essential oil treatment called Equine Raindrop Therapy on horses like yours to stimulate their immune system. It is a lot of fun. Sometimes I just do a mini raindrop on their front legs along the lung meridian, which runs down the inside of the leg. I also wet their hay with each feeding, and keep them on Breathe Easy herbs from Silver Lining, sometimes in combination with their Immune formula. I have also had good luck with a product called Mushroom Matrix ( that balances the immune system and promotes healthy respiratory and vascular systems.


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