Photo by Sarah Coleman
Q: I recently purchased a female donkey from a woman who said she had rescued it from a "bad situation.” The donkey’s neck seems to flop over, though it doesn’t seem to bother it at all. Why did this happen?
A: Your donkey has what is called a fat neck roll or a "broken crest.” Rather than a result of a damaged nuchal ligament, which is the long band running from the base of the skull to the withers that supports the head and neck, excessive fat deposits along the crest create this condition.
It might seem unusual for an animal that is not overtly obese to develop such profound fat deposits, but donkeys, in particular, seem predisposed to such deposits. In addition to the neck, deposits can occur on the tail head and down the top line.
These fat deposits are a result of abnormal carbohydrate metabolism. Donkeys have evolved to survive on low-quality roughage. Many domesticated donkeys, however, are improperly fed—most commonly given a high-energy concentrate, such as prepared grain mix, plain whole or milled corn, or barley, on a regular basis. Not only the feeding of a high-energy concentrate mix but also the quantity fed per head per day can result in broken crest. This type of diet over time can result in a condition called equine metabolic syndrome.
Also seen in horses that are often referred to as "easy keepers,” EMS is a multifaceted condition that begins with chronic feeding of high-energy carbohydrates. It’s likely that your donkey was once overfed a "hot” ration (meaning high levels of carbohydrates/energy) and/or allowed to graze excessively on lush pasture. As a result, its pancreas had to constantly produce high levels of insulin, a hormone that transports glucose from the blood into cells for energy. (It’s also been found that some modern GMO grains, i.e. corn, barley and oats, can result in hormonally uncontrolled high glucose levels.)
Chronic exposure to high levels of insulin causes the body’s tissues to become resistant to the hormone. This means that glucose is not as efficiently taken up and utilized by cells but instead stays in the bloodstream, a condition called hyperglycemia. This faulty metabolism of blood sugar also results in altered fat metabolism, hence the deposits along the crest. EMS is similar to adult-onset Type 2 diabetes in humans.
Although fat deposits are primarily an aesthetic issue, one of the real dangers of EMS is that it predisposes your donkey to laminitis, an inflammation in the foot that can cause lameness. To gauge the severity of your donkey’s current metabolic condition, your veterinarian can draw a blood sample and measure glucose and insulin levels.
It’s important to note the difference between EMS and a similar condition called Cushing’s disease. Cushing’s disease in equines also results in hyperglycemia, but it’s caused by a benign tumor of the pituitary gland that results in an increase in a hormone called cortisol. You can have a thyroid test conducted on your donkey to rule out this potential cause.
There is no treatment for EMS, only management, primarily through diet. The diet of an equine with EMS should be severely restricted in concentrate consumption. Many donkeys can consume enough calories from grass hay alone to maintain adequate body condition. In addition to restricting or even removing grain from your donkey’s diet, pasture management should be a priority. Lush grass and even large consumption of moderate-quality pasture could put your donkey at risk for laminitis. Controlling grass intake by utilizing strip grazing, a grazing muzzle or limited turnout might be necessary. As with all farm animals, consult your vet about the best ways to specifically manage your donkey’s diet in order to tailor to its needs and your farm’s resources.
Unfortunately, a broken crest will remain "broken” and will never be upright, despite a good EMS management plan. On a positive note, however, such a condition does not cause the animal pain. Donkeys are incredibly smart, stoic and hardy creatures, and despite its metabolic condition, you’re highly likely to enjoy many years with your new friend.
About the Author: Anna O’Brien, DVM, is based in Germantown, Md.
Dr. Lyle G. McNeal is a livestock specialist in the Department of Animal, Dairy and Veterinary Services at Utah State University.
This article originally appeared in the March/April 2014 issue of Hobby Farms.