11 Feb Dr. Rachel Fraser on Equine Metabolic Disease
When you think about our population of horses, I think everyone can agree that horses are living longer lives, and many owners are invested in keeping their animals in athletic work and having an excellent quality of life well into their middle age and senior years. With an aging population we are seeing an increase in the number of cases of horses with “metabolic” problems. These can be broken down into 2 main disorders, which have similarities, but have much different causes. There is much research being done into both Equine Cushings disease (PPID) and the more newly defined Equine Metabolic Disease.
Equine Cushings disease (more correctly known as PPID) is a disorder caused by a hormone secreting tumor of the pituitary gland, causing hormonal imbalances. The signs can vary in different horses, but the hallmark symptoms tend to be a long, wavy hair coat that is often resistant to shedding, excessive sweating, lethargy, poor performance, recurrent laminitis, infertility, muscle wasting, abnormal fat distribution, increased drinking and urination, and a weakened immune system (delayed healing, susceptibility to infections). This disease tends to occur in horses over age 15, and has symptoms which worsen over time. Historically diagnosis has been made by clinical signs (long wavy hair coat) but newer blood tests now enable us to detect changes much earlier in the disease. Management of Equine Cushings does become a life-long commitment but we have seen horses have remarkable improvement in quality of life with treatment. The approved treatment is a once daily tablet of the drug pergolide which focuses on reducing the amount of ACTH and other hormones secreted by the pituitary. There is a wide array of nutritional supplements available (many more than can be discussed in this short article), most of which are unlikely to pose risk and may or may not be helpful. Much of the research on supplements is coming out of the human medical side. As most of the affected horses are also insulin resistant, minimizing sweet feeds and other feeds high in soluble carbs is generally beneficial.
Equine Metabolic Syndrome has been applied to those obese, chronic laminitic adult (but often younger) horses we have always referred to as “easy keepers”. Everyone knows that one mare (or gelding) who seems to gain weight by simply breathing. These horses have excessive body fat, and are often officially diagnosed during a laminitic episode. We know these horses do not show improvement when given the medication for Cushings disease which has led researchers toward diagnosing this as a unique condition. Currently treatment is based on reversing the obesity and insulin resistance through a modified diet with strictly limited soluble carbohydrates, and exercise as possible. There are many new grain products available with a low NSC for feeding metabolically challenged horses, a good quality grass hay, restriction of treats, often a grazing muzzle or complete pasture restriction. The adipose cells in excessive fat deposits are very inflammatory, and can cause recurring bouts of laminitis as well as other inflammatory conditions.
If you suspect either of these in your horse please consider asking about testing and potential management changes which would be beneficial during your next appointment.