OklahomaHorses Magazine July 2021

July/August 2021 • OklahomaHorses 11 Obesity in Horses By Dr. Kris Hiney | Equine Extension Specialist | Oklahoma State University O besity is not just a problem in humans but in our pets and horses as well. It is estimated that as many as 50-60% of horses in Europe and North America are obese with many owners not even recognizing their horses are overweight. Recently, this was even demonstrated in horse show judges, which consistently rank horses as moderate condition when they are, in fact, overweight. Ponies, which are most likely to suffer the ill effects of being overweight, are also the most misinterpret- ed as being acceptable when they really are not. This has led to obesity-related health problems increasing in frequency in our equine partners. So why is obesity in horses such a prob- lem? It may help to think about where the horse started. Horses grazed unimproved or native range land where they needed to eat continuously and move throughout the day to meet their caloric requirements. Ever seen an obese, free-roaming mustang? It just doesn’t happen. Now our horses live in pastures with grasses or forages developed for maximal yield and nutrient concentration or are fed hays harvested at the optimal time, again for the highest quality. Busy schedules may also result in far less time to devote to riding. Often, the richness of the diet and the lack of exercise combine to create an unhealthy condition. Why is obesity so hard to recognize in horses? There may be a few factors at play, but, certainly, we are much more aware of and consider an underweight horse as neglected and requiring intervention. The acceptability of larger body types in humans may bleed over into horses. We know many pet owners fail to recognize when their dog or cat is overweight, so horses don’t come as any great surprise. Plus, there is certain joy or satisfaction in feeding a horse with the accompanying nickers of happiness. Owners simply do not see an overweight animal as a management concern, despite the knowledge that, at least in dogs, obesity can remove as much as two years from their lifespan. Obesity in horses should be considered as a management problem. Excessive weight can equal extra wear and tear on the horse’s bones, tendons and ligaments, which may limit his performance ability. Extra body weight also seals in the heat and makes it harder for horses to thermoregulate or cool themselves properly. In Oklahoma, this can certainly be an issue in the summer. But be- yond these rather practical issues, excess fat or adipose tissue can create very real health problems. Adipose tissue is not just an inert glob of fat storing away excess calories but also serves as an endocrine organ. It not only responds to hormones, but it also secretes hormones, cytokines and other bioactive factors. These adipokines have been impli- cated in creating low-grade inflammation, which can contribute to a variety of disease states, including arthritis, cardiovascular disease, insulin dysregulation, laminitis and even PPID. We even know that some obese states can be more problematic than others. Just as in people, where horses store fat can be influential in disease states. Hors- es that store fat in the crest of the neck, through the abdomen and over the tailhead are most likely to suffer debilitating effects of obesity. A cresty neck score is actually a useful predictor of insulin dysregulation. WHAT TO DO Unfortunately, it is often easier to solve the problem of a thin horse rather than an overly fat horse. With the proper feed and a good budget, thin horses can always gain weight. Combining weight loss with the desire to maintain the health of the horse’s digestive tract as well as their mental health can seem to be opposing goals. Horses on restricted diets can develop boredom and frustration behaviors, which can lead to development of stereotypies such as cribbing. Restricting the amount of time a horse spends chewing and salivating can also result in the development of ulcers. Even the very metabolism of a fat horse may be working against an owner. After all, they didn’t get there magically! Often, these horses have a reduced met- abolic rate or are essentially metabolically more efficient than their lean peers. They also may have an increased appetite and are just more likely to consume more when offered ad libitum feed or left to graze in a pasture. In a recent study, restriction of horses to 60% of their maintenance requirement for 28 days did not alter the horse’s body condition score. Of course, there may be issues with