Effects of Obesity in Horses

Obesity in domesticated animals such as horses has been on the rise and now some even consider it an epidemic. Horses are normally grazers feeding mostly on grasses and traveling rather long distances to be able to find adequate nutrition. Domesticated horses are typically fed grass or alfalfa hay supplemented with high fat and sugar content grains. These, along with the fact that most domesticated horses do not partake in adequate exercise either under saddle or on their own in a pasture has contributed to this rise in obesity in horses.

I work for a primarily equine veterinary service and probably about 95% of the horses we see are moderately to severely obese and their owners tend to deny it and say they look healthy. This is scary because obese animals, not just horses, are at an extremely higher risk for illnesses and pain. In many animals including horses, obesity has been linked to an increased insulin resistance, which can cause many problems. In horses, some common illnesses include colic, laminitis, and Cushing’s.

Colic is a general term for abdominal pain. Horses that eat high fat and sugar diets like grains are at a higher risk for getting colic although causes for colic are wide spread and difficult to determine. These can vary from just a little stomach ache where they go off feed, to a more serious dehydration problem and possible a twist or flip of the intestines cutting off circulation and requiring surgery. Colic is a very common disease in horses and thousands of horses die every year as a result of colic.

Laminitis is a severe condition caused by the breakdown of lamellar tissue in the hooves of horses. The breakdown of this tissue can put more pressure on the hoof and the coffin bone (the bone inside of the hoof). This can cause the coffin bone to begin to rotate toward the ground causing severe pain. In some cases, the rotation can be so bad that the tip of the coffin bone pokes through the bottom of the hoof resulting in the horse needing to be euthanized. Connections have been made to insulin resistance and obesity because when they are eating high glucose diets and they are insulin resistant, their blood sugar increases and can cause lots of damage including that contributing to laminitis.

Cushing’s disease is a disease that occurs when there is damage to the pituitary causing an enlargement, which puts pressure on surrounding brain tissues causing a decrease in functions. Another factor is that the pituitary secretes an excess amount of ACTH and subsequently cortisol. As you can imagine from our discussion in class about these hormones, they can cause a lot of damage when in high doses for extended periods of time. Some consequences are excessive coat growth and inability to regulate body temperature, a depressed immune system, lethargy, and some neurologic symptoms as well. This can be a very serious disease and is very common in older horses.

As you can see, obesity can cause a wide range of serious side effects in horses. This is not only the case in horses, dogs, cats and other domestic animals are also suffering from obesity. Since this is something that we as animal owners have caused by poor nutritional and exercise practices, this is also something that we have the power to prevent by changing the way that we treat our animal friends. This is also a serious problem for humans and something that we should consider for ourselves as well because we can prevent a lot of pain and suffering. Another issue that I think we should look at is why we have this inability to determine when ourselves and our animals are overweight. Any thoughts?

Philip J. Johnson, B.V.Sc. (Hons), M.S. DACVIM, DECEIM, MRCVS,¹ Charles E. Wiedmeyer, D.V.M., Ph.D., DACVP,² Nat T. Messer, IV, D.V.M., DABVP,¹ and Venkataseshu K. Ganjam, B.Sc., B.V.Sc., M.S., Ph.D., M.A. (2009). Medical Implications of Obesity in Horses—Lessons for Human Obesity.