By Dr. Heather Beach DVM
When determining the optimal diets for our horses, there is a standardized way of measuring the current and ideal weight of a horse through the use of the body condition score, or BCS. The standard body condition scoring scale for horses ranges from a 1 to a 9, with 1 being emaciated, 9 being morbidly obese, and 5 to 6 being ideal. The score for an individual horse is generally reported as a 5/9 meaning that the horse has a score of 5 on a scale from 1-9. Even with this standard well documented, horse owners still experience a great deal of confusion and anxiety about the ideal weight for their individual horse.
As a horse owner, you should be objective when assessing your horse’s weight, and listen carefully to the advice and input of your veterinarian when discussing your feeding program. Many people will irrationally equate feeding their horses (and other pets) with loving them, and as a result, obesity in horses and other domestic animals is extremely common. It is important to remember that the health consequences of having an overweight horse are oftentimes FAR more severe and dire than having a slightly underweight horse. An obese horse puts more stress on its joints, tendons/ligaments, and hooves. Most importantly however, obesity in horses causes a cascade of metabolic changes which greatly increase the chance for the development of laminitis. Laminitis is a painful and frequently irreversible disease of the hoof which often necessitates euthanasia. Just as obesity in humans dramatically increases the risk for a fatal heart attack, obesity in horses can have deadly consequences due to laminitis.
Your veterinarian can help you objectively determine your horse’s current body condition score and will take into account his/her breed, level of athleticism, and medical history to determine if the current score is the most appropriate one for your horse.
The BCS Chart can be used to identify areas of fat accumulation in the horse and will help
you learn how to accurately body condition score your own horse:
2. Crease down back
4. Along the withers
5. Along the neck
6. Behind shoulder
The ideal body condition score is between 5 and 6.
Horses in the 5-6 range will have some fat under the skin in the areas shown in the diagram, making those areas slightly prominent and spongy to palpation. If you notice any large accumulations of fat on your horse in the areas outlined in the diagram, chances are your horse is overweight and in danger of serious health consequences. If your horse is underweight, the areas noted in the diagram may appear sunken and bony prominences may be more visible.
It is important to note that the size of the horse’s belly is NOT an indicator of body condition. Humans, predominantly adult human males, do have a tendency to accumulate intra-abdominal fat. This fat is stored within a special abdominal connective tissue called “omentum” and is responsible for the uniquely recognizable “beer belly” appearance (i.e., Santa Claus and his belly that shakes like a bowl full of jelly, or Homer Simpson). For the most part however, fat stores in people and animals are most extensive just underneath the skin and covering muscle (like the fat at the edge of a pork chop or a steak).
If your horse has a particularly round and distended abdomen, it is much more likely to be due to a “hay belly.” A hay belly has a couple of different contributing factors, but is predominantly caused by physically having a large amount of ingesta or partially digested food sitting within the large intestinal viscera of the horse.
The intestinal viscera, particularly the large colon and cecum of the horse take up a tremendous amount of space within the abdomen. If there is a large volume of feed or gas within the viscera, it stands to reason that the abdomen will appear more distended and “larger”. Coarse first cut hay which tends to be more fibrous and “bulkier” will further expand a hay belly.
This distended abdomen may also appear “pendulous” and hang downwards considerably in horses with a poor topline and weak abdominal muscles, or in broodmares who have had foals in the past. A horse who is unfit, or who is not ridden in a manner that strengthens his core (topline and abdominal muscles) will have a “saggier” belly and may be mistaken as “fat” by the owner.
Different breeds of horses tend to be naturally leaner or heavier than other breeds. Do not be worried if your lean and athletic off the track thoroughbred does not ever seem to get above a body condition score of 5. Likewise, it may take a great deal of effort to get your Hafflinger pony DOWN to a body condition score of 6.
Equine Metabolic Syndrome
It is important to note that horses suffering from Equine Metabolic Syndrome may paradoxically have large fat deposits and ribs showing at the same time. Equine Metabolic Syndrome (EMS) is the name given to describe horses who have become insulin resistant and thus have a difficult time processing sugars/glucose from the diet. Horses with EMS and insulin resistance are at the highest risk of having an episode of laminitis. These horses may show extreme “regional adiposity,” meaning very large accumulations of fat in the areas highlighted on the BCS chart. The presence of the fat on the horse’s body further exacerbates the insulin resistance. Owners may be aware and work hard to limit starches and sugars in the diet, often resulting in weight loss. It may be difficult to get the horse to lose the fat deposits in a severely insulin resistant horse, resulting in a slightly “ribby” horse with large fat deposits. Horses with this appearance need to have their diet very closely managed to minimize chances of having a laminitic episode.
The Role of Exercise
Regular exercise improves your horse’s insulin sensitivity and helps maintain a happy balance between muscle and fat. Just as in people, there is no dietary shortcut for exercise. Regular work is good for your horse, especially if his/her turnout is limited. A horse who is in full regular work can tolerate a slightly higher body condition score since exercise will improve insulin sensitivity. A word of caution to all the show riders who like to keep their working horses on the “plump” side, however. A horse who is overweight but in consistent work may be a compensated insulin resistant horse. If injury or illness causes the horse to come out of work for a protracted period of time, they may become decompensated and suddenly be at risk of developing laminitis.
Another important consideration for sport horses — underweight horses will struggle to put on and maintain topline. Lean horses who do not put on muscle most likely need additional calories. Most of the time this need can be met with more or better quality forage (hay) but there can also be a deficiency of essential amino acids like lysine, Vitamin E, or the horse may have an underlying muscle disorder such as PSSM that will respond to added fat in the diet. A full veterinary workup for underweight horses includes a thorough oral exam, diet and work history, fecal exam, and may involve gastroscopy to check for gastric ulcers, testing for Cushing’s Disease depending on the age of the horse, Vitamin E and Selenium levels and/or general bloodwork and tests for infections diseases like Lyme disease or EPM.
If you have any questions about your horse’s body condition or risk factors for developing laminitis, discuss them with your veterinarian.