Hay everyone!
I certainly hope spring is right around the corner here in NJ! The weather has been warming up recently, so I’m hopeful I’ll be seeing some green pastures soon. This week, I did some digging into metabolic and nutritional disorders that can affect horses. I decided it would be best to cover two of the more well-known conditions: equine metabolic syndrome and pituitary pars intermedia dysfunction (also known as equine Cushing’s disease). The overlap between these conditions can get a bit confusing, but never fear, Lord Nelson is here! We’ll go through them together and y’all will be experts in no time.
Before we dive in, I just wanted to remind you to please consult your veterinarian for individual concerns about your horse. This blog is just for informational purposes; have a chat with your veterinarian if you think your horse needs extra care. I’ll be covering a description of the condition, how it could be caused, the clinical signs, how it is typically diagnosed, and how it is treated or managed.
Equine Metabolic Syndrome (EMS)
EMS is a collection of issues associated with insulin dysregulation, increased deposition of fat, and lowered ability to lose weight. Insulin is like a key that unlocks the body’s cells and allows glucose (a specific type of sugar) to enter. The cells break down this glucose to get the energy they need. “Insulin dysregulation” is a general term that means the body has trouble making the right amount of insulin or the insulin no longer “unlocks” the cells like it used to. When this happens, like in horses with EMS, the glucose can’t get into the cells.
Causes: Some breeds of horses are more likely to have EMS than others. These tend to be horses that were bred to survive in harsh environments, like Arabians and mustangs, as well as donkeys and ponies. Their bodies store glucose really efficiently as a way to prepare for times when food might be scarce. Today, these horses generally have access to a constant source of food, and they end up eating too much.
Signs: Some of the clinical signs of EMS include: a high body condition score (usually >6 on a 9-point scale), excess fat on the neck (making it have a “cresty” appearance), and an abnormal insulin response to glucose.
Diagnosis: To officially diagnose a horse with EMS, a veterinarian will use a blood test to observe how the body reacts to glucose. For example, during an oral glucose test, the veterinarian will give the horse a dose of oral glucose powder. Then, they will draw blood 60 minutes and 90 minutes later and measure the concentrations of insulin and glucose in the blood.
Management: Unfortunately, there is no cure for EMS, but it certainly can be managed. The main way is through diet, which involves limiting the amount of non-structural carbohydrates (think sugars) that the horse eats. This can be done by reducing the time a horse spends grazing on pasture or by using a grazing muzzle.
Pituitary Pars Intermedia Dysfunction (PPID)
Let’s break down the name of the condition: “pituitary” refers to the pituitary gland, “pars intermedia” is a specific region in the pituitary gland, and I’m sure you know that “dysfunction” means something isn’t working correctly. In mammals, there is a structure in the brain called the “pituitary gland” that controls the release of many hormones into the body. If this gland isn’t working properly and the release of hormones isn’t controlled, then the effects can be widespread in the body.
Causes: PPID is an age-related condition. It is most often diagnosed in horses over 15 years old and is very rare in younger horses. Over time, the neurons that connect to the pituitary gland start to break down and can no longer send signals about when to release hormones.
Signs: Some of the most common clinical signs include: a long and curly hair coat, loss of muscle, increase in thirst, and excessive urination. Horses can have both PPID and EMS at the same time, so it’s important to consider the signs of both conditions.
Diagnosis: Like EMS, PPID is diagnosed using blood tests. For example, a blood sample can be analyzed to determine the concentration of adrenocorticotropic hormone (ACTH) present. This hormone is produced by the pituitary gland and released into the bloodstream. It is important to note that the concentration of this hormone can be impacted by outside factors, including season (the concentration tends to be higher in the fall), stress, illness, exercise, and sometimes diet.
Management: Although there is no cure for PPID, there are lots of ways to manage the symptoms. Some medications are available, but their success is highly dependent on individual cases and continuous monitoring of the dose. In cases where a horse is overweight, diet and exercise can help improve symptoms. Regular preventative care, like routine vaccinations and dental work, is also really important because horses with PPID have a decreased immune response.
Wow! I certainly learned a lot from my research, and I hope you learned something today too. Metabolic and nutritional disorders are a really big topic in equine research. There are still a lot of open questions, but maybe someday you’ll be the one to find the answers!
Until next time.
Your friend,
Lord Nelson