10/22/2024
Equine Body Condition: From Too Fat to Too Thin to Just Right
October 21, 2024
Posted by Stacey Oke, DVM, MSc
Here’s how to determine if your horse is under- or overweight and, if so, by how much.
Assessing your horse’s condition and feeding strategies for reaching a body condition score of 4 to 6.
Equine obesity runs rampant in our industry, with some studies suggesting up to 54% of domestic horses fall into the overweight or obese category (Golding et al., 2023). Excess weight can lead to significant health and welfare issues, notably increasing the risk for developing endocrine-associated laminitis. On the flip side, owners of hard keepers might bristle at overweight horses getting all the attention because even underweight horses have important health issues that need to be addressed.
Regardless of whether a horse is under- or overweight, the underlying cause of the weight-to-horse mismatch is usually an imbalance between the supply of energy the horse receives and the energy he expends. This imbalance can be due to either nutritional or non nutritional factors, or even a combination of both. And while both factors need to be addressed, the first step in managing any horse’s weight is to determine if your horse is under- or overweight and, if so, by how much.
Assessing Equine Body Condition and Weight
Body Weight
The most accurate way to measure body weight—what the horse weighs in pounds or kilograms—involves a scale. While some horse owners are fortunate enough to have access to scales, most do not and must rely on other tools to help estimate body weight, including weight tapes and equations.
“Weight tapes for adult light horses are readily available and easy to use,” says Krishona Martinson, PhD, professor and equine extension specialist at the University of Minnesota, in Minneapolis. “While weight tapes tend to be less accurate than equations, if used properly and consistently, they can be used to estimate body weight and detect changes.”
As for the equations, Hall developed the first in 1971, which uses girth circumference and body length to estimate horses’ body weight. “For light horses, the equation is girth circumference (inches) x girth circumference (inches) x body length (inches) divided by 330,” says Martinson. “Additional equations with different denominators have been developed for Arabians and ponies by other researchers.”
More recently Martinson and colleagues (2014) used breed type, girth circumference, body length, neck circumference, and height to develop body weight equations for nine different breed-types of horses. Martinson says those equations are more complicated but tend to be more accurate than previous formulas and weight tapes. To help owners make these calculations, Martinson and colleagues developed the Healthy Horse app.
“I often recommend the Healthy Horse app,” says Kris Hiney, PhD, associate professor and extension specialist at Oklahoma State University, in Stillwater. “Of note, it has a separate equation for Thoroughbreds, which is important in this breed where owners often struggle to get them to consume enough. Thoroughbreds just don’t have the genes for a big appetite like some of the other breeds.”
Just knowing the horse’s body weight, however, does not tell you whether he is over- or underweight. This is where you incorporate the body condition score (BCS).
Body Condition
Free Download: Equine Body Condition Score Poster
Body condition score offers a subjective assessment of adipose (fat) tissue across specific areas of the horse. The nine-point Henneke scale ranks among the most common methods for assessing BCS. It involves appraising adipose tissue in six anatomic areas using palpation: neck, withers, behind the shoulders, ribs, back, and tailhead. The scale spans a range from 1 (extremely thin) to 9 (very fat), with an ideal body condition considered a 4 to 6.
Once you know whether a horse is over- or underconditioned, you can use both body weight and BCS to follow his weight-loss or -gain journey, guiding and celebrating progress. You’ll also need the horse’s body weight for calculating how much hay and other products to feed to meet his nutrient requirements (described in a moment).
Non nutritional Factors With Weight-to-Horse Discrepancies
As mentioned above, horses can become over- or underconditioned when their diets provide excessive or insufficient calories compared to their energy needs. But before jumping into the diet, experts recommend evaluating the horse for non nutritional factors that can affect condition.
Non nutritional Factors in Underweight Horses
With underweight horses, a veterinarian needs to perform a complete history and physical examination to determine if the weight loss is acute or chronic and to identify and address underlying diseases, such as:
Endoparasitism
Gastrointestinal disorders causing malabsorption or equine gastric ulcer syndrome
Organ dysfunction (e.g., liver or kidney insufficiency)
Endocrine disorders such as hyperthyroidism or pituitary pars intermedia dysfunction (PPID, formerly called equine Cushing’s disease)
Chronic conditions such as equine asthma or musculoskeletal disorders, including osteoarthritis (OA)
Jarvis and McKenzie III (2021) reported other important Non nutritional considerations, including dental disease that hinders acquisition and chewing of food as well as social stress.
“Pecking order is a huge factor in contributing to underweight horses,” says Hiney. “Owners and managers really need to pay attention to that. The more subordinate or older the horse, the easier they are to push off feed. I recommend that seniors or harder keepers have separate areas to consume the higher-calorie portion of their meal (grain or soaked feed).”
Osteoarthritis deserves further mention because horses with OA, including in the neck, often show reluctance or take longer to eat off the ground. They might even struggle to pull hay from a hay net.
Hiney adds, “OA is a huge concern. Again, it pushes the horse down the social ladder so they may not be able to forage as easily.”
Non nutritional Factors in Overweight Horses
When managing overweight horses, consider endocrine (hormonal) conditions such as equine metabolic syndrome and PPID. Identifying and addressing these conditions play a crucial role in achieving successful weight loss.
Nutritional Approach to the Under- and Overweight Horses
skinny horse grazing
Be patient with underweight horses; it can take a few months for them to put on condition,
especially if they are recovering from a body condition score of 1 or 2. | Adobe stock
With a solid idea of the horse’s current weight and BCS, and the nonnutritional factors managed, we can get down to brass tacks: feeding to condition in an otherwise healthy horse.
Feeding the Underweight Horse
Here are some tips Hiney recommends when feeding underweight horses:
Assess how much you are feeding them. “A lot of people underestimate how much these horses need to eat. I always recommend weighing the feed,” Hiney says.
Offer hard keepers ad libitum (fed without restriction) good-quality hay. She acknowledges forage can be difficult to manage, especially because owners are sometimes limited on the type and quality they can purchase in their region.
To start adding weight, Hiney says owners can try adding 5 pounds of alfalfa cubes to the daily ration. “Then we can talk about the feed and choosing a higher-calorie feed,” she says. “I typically suggest rice bran or beet pulp as a good add-in.”
Increase the number of meals (at least to three rather than just two) to increase the calories from concentrates.
Complete feeds, which contain everything your horse needs in his diet, including the forage, are expensive but can be a great option for seniors or tricky cases where the horse has an irritable bowel. Price could be an important consideration in the case of complete feeds.
Hiney warns owners of underweight horses to be patient. “It can take a couple months to recondition an underweight horse or even longer if we are recovering from a BCS of 1 or 2,” she notes.
A horse can gain up to 3 pounds per day, but you cannot visually detect weight gain under 100 pounds in a 1,000-pound horse. For example, you might have to wait three months to see a gain of 300 pounds.
Feeding the Overweight Horse
“Addressing excess condition can sometimes be as simple as starting to weigh the hay,” says Martinson. “Most adult horses should be fed about 2% of their body weight each day in forage. For a 1,000-pound horse this equals 20 pounds each day.”
If owners do not weigh the hay, they do not actually know how much their horses are receiving.
“Weighing hay is not hard but can be time consuming,” she adds. “Owners can purchase an affordable (approximately $20) hanging scale and use a tarp or hay net to confine the hay during weighing. Weighing hay is essential for owners managing overweight horses.”
For weight loss Martinson recommends reducing the amount of hay to 1.75% of body weight, but never below 1.5% body weight.
“Overweight horses should also be fed a lower-energy hay to help induce weight loss,” she adds. “For example, a more mature grass hay will have significantly less energy than alfalfa hay. And owners also need to replace energy-dense grains with a ration balancer and reduce or eliminate access to pasture. Overweight horses still have vitamin and mineral needs, hence the recommendation for a ration balancer.”
Even though we’re looking for weight loss, Martinson recommends feeding several small meals throughout the day. She says horses would ideally spend at least 16 hours a day chewing to ward off formation of gastric ulcers.
“Offering ‘busy hay’ is a good part of the weight management plan,” she adds. “Busy hay is very mature hay that takes the horse longer to ingest. The maturity reduces the caloric density while taking the horse longer to chew. A few pounds of busy hay, along with their normal hay ration, as well as a hay net can help ensure horses on a weight-loss plan have something to chew on.”
In terms of progress, Martinson recommends horses lose weight slowly.
“Horses on a good weight-loss plan should lose about 1 BCS each month until they reach their desired BCS and body weight,” she notes.
Troubleshooting Your Horse’s Body Condition and Weight
Simplistic in design, the 9-point Henneke BCS system relies on subjective assessment. Some owners over- or underestimate their horses’ condition using this tool. In her own research Martinson has shown that horse owners miscalculated the weight of their horses by 7 to 15%.
Further, some owners find the 9-point scale technical and challenging to use. For example, 60 owners participating in a small study by Golding et al. (2023) reported the scale wasn’t applicable to all breeds, types, ages, or sexes and that additional photos would be helpful. Further, some owners indicated they were unfamiliar with certain body parts, such as the tail head, hook bones, and loins. Even after owners received training on how to use the 9-point Henneke BCS scale, Golding et al. reported no improvement in owners’ accuracy in BCS judgment compared to an expert’s opinion.
photo of an overweight bay pony with cresty neck
Peer pressure appears to influence owners’ perception of their horses’ condition. For
example, a barn full of obese horses normalizes this state.| iStock
Golding et al. (2023) reported that horse owner impressions of weight-loss and
-management strategies as cruel create a barrier to battling bulge. Ross et al. (2024) similarly reported that owners felt they had to “choose between their horses’ mental and physical health when making decisions related to weight-management strategies.”
“However, research from Maryland and Minnesota shows that grazing muzzles do not impact the stress hormone cortisol or result in other physiological stress measures in Miniature or stock horses (tinyurl.com/3k3aau5t),” says Martinson.
Additionally, peer pressure seems to affect owners’ ability to recognize their horses’ true condition. For example, a barn with many overweight horses could create an “obesogenic environment,” where people view excess condition as normal (Golding et al., 2023).
“My research group conducted a study on BCS years ago and found a wide variety of opinions on the same horse,” says Hiney. “The concern really is how are we training people. It is imperative that owners get their hands on the horse and have someone give feedback on their technique. You truly need to feel the horse, give each section (of the body assessed) a number, and then average it, which you can’t do from pictures,”
Golding also reported that some owners felt aware their horse was over conditioned but did not feel in control of the situation and, therefore, did not know how to address their horses’ BCS. As Ross et al. reported, “It is critical to shift the societal paradigms surrounding horse weight and work collaboratively with owners to develop tailored solutions that meet their horses’ specific needs.” These strategies need to be practical and align with the owners’ beliefs, especially if sacrifices.
Take-Home Message
Owners should take every step possible to recognize and achieve an appropriate weight and condition for their horses to optimize health and welfare. “Perhaps most important is to frequently repeat the assessments (monthly, for instance) to stay on track towards the goal,” says Martinson. “It can be hard to notice changes over time when you see the horse on a daily basis.”
