A look into metabolic issues faced by modern equines
Written by Dr. Emily Zakrajsek
Who are you calling chunky?
Sadly, with the development of higher quality hay and pastures, the increased numbers of non-worked equines (lovingly referred to as “pasture puffs”) and the human need to show love and affection with food, the percentage of horses, ponies and donkeys that are overweight has become higher and higher over the past decades. This prevalence has become so high in fact that many of us can no longer accurately recognize if a horse is overweight as we have become accustomed to seeing them as such. Donkeys and miniature horses are especially overlooked in this regard because we blame the “chunkiness” on their small stature. It is also important to remember that donkeys and minis originated in very harsh environments and had hard working jobs. Therefore the life of being a pet and getting fed calorie-dense foods can quickly lead to obesity.
What’s so bad about the curves?
Although a horse who’s a bit chunky can be considered cute, the truth is that being overweight can be a huge detriment to their health. Overweight horses are at a much higher risk for osteoarthritis, cardiovascular disease, laminitis and several metabolic diseases. All of these can lead to discomfort and shortened lifespans. In particular, laminitis (often associated with one of the 3 metabolic disorders: Equine Metabolic Syndrome, Insulin Resistance or Equine Cushings) can be crippling to the point of necessitating humane euthanasia.
How do I know my horse is fat?
Having your veterinarian perform a Body Condition Score is a routine part of any physical examination. This standard score chart assigns the horse a number, usually between 1 and 9 with 1 being extremely emaciated and 9 being obese. It is important to note however that horses with metabolic disorders specifically can develop fat deposits at specific areas, while the remainder of their bodies may be normal. Adipose tissue found in 3 specific areas (neck crest, behind the shoulder and at the tail head) have been shown to produce their own hormones, acting somewhat like their own endocrine organ. This becomes hugely problematic as these hormones can react with normal body hormones and confuse the body’s regular systems, further adding to the development of metabolic diseases.
The 3 musketeers of metabolic disease
As previously alluded to there are 3 main metabolic disorders we can see in equines: Equine Metabolic Disease (EMS), Insulin Resistance (IR) and Pituitary Pars Intermedia Dysfunction (PPID, also known as Equine cushings). These 3 diseases often go hand in hand but can also occur as singular issues or any combination of the 3. Each one requires slightly different management and pharmaceutical treatments in order to reduce the risks of chronic issues such as laminitis, obesity, arthritis etc. Although any one of these diseases can lead to obesity it is also important to remember that they can also be triggered by being overweight. To reduce one is to reduce the chance of the other and vice versa.
In PPID, ACTH levels (a hormone produced in the pituitary gland) in the blood are elevated. Some symptoms include hair overgrowth, difficulty maintaining a topline and most importantly a reduced ability to fight infections due to immune system depression. Although horses with PPID aren’t always overweight they can have the same risks for the development of laminitis. Treatment for Cushings is a daily medication called Pergolide (brand name prascend). Although this medication can be expensive and is required long term it greatly improves the quality of life for horses with Cushings and increases their life expectancy.
With Insulin Resistance the insulin and sometimes glucose levels in the blood are elevated. Horses with this condition are unable to process sugars properly and so are at increased risk for obesity, “tying up” (painful muscle spasms) and laminitis (aka founder). These horses require not only dietary management but can sometimes be so severe that they require a drug called Metformin which is also used in human diabetics to help with sensitizing the body’s cells to insulin so they can uptake glucose from the blood. This drug must be scripted out to your human pharmacy. Depending on dietary management this medication may or may not be needed long term or at all. Horses with insulin resistance should be on a diet that is composed mostly of grassy hay (the less rich the better) along with a low sugar mineral supplement (e.g optimal or equalizer) and a source of dietary fat (corn oil, vegetable oil, canola oil etc). This ensures adequate nutrition without causing spikes in glucose levels. Pasture, treats and excess grains should be avoided.
Finally, in Equine Metabolic Syndrome the Thyroxine levels in the blood are decreased. Horses with EMS have lowered metabolic rates than the normal horse due to decreased levels of the active thyroid hormone, Thyroxine. Similarly to horses with Insulin Resistance these horses can often be managed with diet alone {see dietary recommendations above}. In EMS horses who are already obese or show areas of “dangerous adipose tissue” (neck crest, shoulder fat pad, tailhead fat) a few months on a medication called Levothyroxin is recommended to aid with priming the metabolism and losing weight. In time they can often be weaned off this medication but by reducing the dangerous adipose we greatly reduce the risk of laminitis in the future along with weight/inflammatory- related arthritis.
The Whole Picture
When it comes down to it, an overweight horse is one who has their health compromised. By reducing excess caloric intake, especially in our non-working equines, to ensure a healthy body condition we can greatly reduce the risks of many health concerns. If you are unsure about the current weight-to-health status of your equine friend do not hesitate to reach out and book an appointment with your veterinarian!
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