Learn how nutritionists took 3 horses from fat to fabulous

Suggest a horse is at risk for colic, and people jump into action. Tell someone their horse is overweight, and the reaction can be different. Some owners might be in denial about their horses’ extra body condition, others even consider it an insult. However, equine obesity is a growing problem. Extra weight makes it harder for performance horses to jump, run, or turn. Obesity can also increase any horse’s risk for developing health problems such as laminitis, equine metabolic syndrome, and heat or exercise intolerance.

“Overweight horses require a little extra attention, but obesity is fixable and can be treated like any other health problem,” says Lori Warren, PhD, PAS, an associate professor of equine nutrition at the University of Florida, in Gainesville. “If somebody is telling you your horse is overweight and that losing a little can alleviate a problem, you should take that seriously and not personally.”

Weight’s Impact on the Equine Body

Many researchers have examined the link between obesity and arthritis in horses and other species. The jury is still out if obesity alone can cause arthritis, says Jennie Ivey, PhD, PAS, an associate professor and extension equine specialist at the University of Tennessee, in Knoxville. However, added weight does increase systemic inflammation. 

“The impact on the joint itself is still under review, but studies have shown horses are in a higher inflammatory state when they are overweight,” she says.   

Warren added that overweight performance horses already exert extra stress on their joints, potentially exacerbating arthritis. Inflammation is part of exercise, and it has its purpose in breaking down tissues and rebuilding them stronger, but in excess the breakdown exceeds the rate of repair. 

“Cumulative inflammation may start the onset of arthritis earlier in life,” Ivey says. “That might mean the horse needs more layup time or gets injured after a misstep because they tire sooner.” 

In 2021 researchers from North Carolina State University found that despite the health risks of obesity, overconditioned horses tend to get rewarded in the show pen. In a survey the study investigators asked hunter judges how they would rate horses based on condition. Most agreed they would penalize an underweight horse more than an overweight one.

Laurie Lawrence, PhD, a professor of equine nutrition at the University of Kentucky, in Lexington, equates this to the old saying “beauty is in the eye of the beholder.” What one person might find to be overweight, another might find to be just right. And that standard appears to be discipline-specific.

“Everybody says a horse should be thus and such, and it really just depends on their job,” she says. “Going to endurance events was an eye-opener for me—the horses were so lean. Most of those horses are a 5, and others a 4. I realized they are like marathon runners. Their arms, legs, and body look skinny because any extra weight carried over miles, miles, and miles makes a difference.”

Defining Overconditioning

The Henneke body condition score (BCS) is the industry standard for determining appropriate condition for a horse. Generally, horses rated 1 through  3 are considered poor to thin. A 4 to 6 horse, described as moderately thin to moderately fleshy, is typically classified as healthy, with a 7 to 9 horse, characterized as fleshy to extremely fat, considered overweight or obese. The BCS alone, however, might not determine a horse’s condition level. Ivey starts with BCS and then considers the horse’s lifestyle, exercise, and underlying conditions. 

“It’s important to go out and feel differences between horses with varying body condition scores,” she says. “One of the easiest spots to use is the ribs. With a body condition of 4, you may see ribs as the horse breathes. At a 5, you might not see the ribs but can easily feel. A 6 means a little more fat cover, but you shouldn’t have to dig to find a rib. If you do that, it puts horses into upper body range scores.”

She recommends the Healthy Horse App created by the University of Minnesota Extension as a tool for getting your horse’s body condition on track. The app helps estimate current and ideal body weight for several breed types by using new equations developed through the university’s research.

Warren says the fat cover over the neck, shoulder, and rump can provide additional clues. If you can see or feel the hip bones, pelvis, and femur, the horse is likely not overconditioned. When a ripple of fat replaces those features, it is a good indicator of condition.

“You might see a horse shown in halter where their body jiggles like Jell-O at the trot. It’s not muscle,” she says. “Body condition scoring should only take fat into account, not muscle structure, so you need to be able to distinguish between them.”

Just as in people, getting horses to shed excess weight isn’t easy. It’s a multifaceted, long-term process. To help guide your journey, here are three examples of how our sources have helped overweight horses slim down.

Case Study 1: Obese Stock Horses

Ivey’s PhD research focused on the process of changing a horse’s body condition score—specifically, bringing an overconditioned horse back to a lower weight. She studied stock horses in a university research and teaching herd. 

The horses were all BCS 8 and considered obese. It took nearly five months to transition them to a BCS of 5. She reduced their calorie intake by 20% based on each horse’s weekly body weight. All horses worked three to five hours each week.

Ivey says she used forage testing and dietary analysis to determine if the horses’ diets met their daily needs and make weight loss program adjustments accordingly.

“By the time the horses got back to a 6 or 5, I got blasted that they looked horrible,” she says. “The thinner, more refined look wasn’t typical for the discipline, and the consensus was that these horses were viewed negatively. For me, it illustrated the difference between how the stock or draft world thinks of overconditioned as compared to Thoroughbreds or endurance horses, where the athletes look leaner and thinner.”

Case Study 2: Laminitic Trail Horse

Warren got called in to help design a diet for a 12-year-old horse with an active recreational rider who trail rode four to five times a week. The gelding had a BCS of 8 and experienced soreness from laminitis. Usually Warren prescribes exercise for weight loss. However, the tissues in this horse’s feet had to heal first.

So she recommended the owner keep the gelding off grass, begin weighing hay rations, and feed him a lower-quality grass hay such as timothy or orchard  grass—readily available near her Florida barn.

“One simple way to help a horse lose weight is by changing the type of hay fed to one that is more mature and less nutritious,” she says. “Feeding a timothy/grass hay that has mature, stemmy, dry seedheads (in place of) alfalfa or less mature hays cuts down on calories and can help a horse who is slightly overweight slim down.”

Initially this strategy resulted in weight loss, but it tapered off after six weeks. Next, Warren recommended soaking the hay an hour before feeding to pull out sugar and calories (being sure to discard the waste water before feeding), which allowed the gelding to shed a few more pounds.

It took nine to 12 months for the ­gelding to lose 150 to 200 pounds and reach a BCS of 5. Warren recalled that he would get visibly mad because he wasn’t out on grass. In an ideal situation the owner would have fed small portions of hay every few hours, but this was impractical around her work schedule. Instead, she fed the soaked hay three times a day using haynets. Once the horse’s feet healed and he returned to soundness, he and his owner got back to trail riding with a graduated fitness program. She has had to maintain his feeding and exercise routine, however, long-term. 

“Often, it is a very individual approach,” says Warren. “But a cautionary tale is that you can’t go back to the scenario that allowed the horse to get overweight. When on pasture full-time or with free-choice hay feeding, some horses just overdo it. That doesn’t mean you can’t allow a little bit of grazing, but it has to be for shorter periods—between one and four hours per day—and restricting at certain times of the year or certain times of the day.”

Case Study 3: Arthritic Western Pleasure Prospect

A veterinarian asked Warren to help with a 19-month-old Western pleasure prospect that needed to lose weight but was currently lame. The veterinarian had diagnosed the filly with early onset arthritis caused by osteochondritis dissecans (OCD) that at some point had corrected itself but left permanent damage in the fetlock.

“She started at about a 7 BCS and, within two months, we were able to bring her down to a 5 to 5.5,” she says. “It alleviated her lameness, and she went on to show and is still out competing.”

Controlling the filly’s intake was key to the success. The owners could keep her stalled for a half day with half-day turnout, giving them more control over what she was eating and when. Also, given the horse’s location in Florida, the sandy soil grew less lush grass than in other parts of the country.

“Ration balancers and low-starch feeds can be helpful tools when the horse is in exercise and has a higher need for nutrients than the average backyard recreational horse,” Warren says. “What I like about ration balancers in particular is that I can adjust a horse’s calorie intake down and provide the minerals and vitamins that may be missing in a more mature forage. Ration balancers take out the grain and grain byproducts, cutting back on calories.”

It’s Not Easy

Helping a horse lose weight requires effort. Warren says weighing out and feeding dry matter versus grazing is a hard pill to swallow because we know horses are healthier grazing and ­roaming.

“Horse owners have to practice a little tough love and resist the urge to feed things that aren’t necessary and take time to weigh out every item that is offered to the horse to better manage their intake,” she says.

Ivey adds, “People often ask about feeding a more ‘natural’ diet, but at an animal science conference last year there was a big discussion about what is a natural diet. The studies showed that what feral horses eat is much different than how domesticated horses are ­managed.”

In the wild, browsing includes eating bushes and herb-type shrubs rather than rich grass or high-protein forage. Because domesticated horses have access to forage with higher nutritional values, a high-quality feed often exceeds what their bodies need.

Lawrence says not responding to decreases in the horse’s exercise or changes in environment sets the stage for gaining too much weight. In addition, many diet changes happen after the horse has gained or lost weight instead of in real time. For­ example, when the show season ends, the horse might continue with the same amount of training but isn’t spending hours traveling to new venues and competing each week and, therefore, does not have the same nutritional needs. 

“A long time ago, someone equated riding in a van or trailer to be similar to walking for a horse,” Lawrence says, referring to the stress on the body. “So eight hours in a van might be the same amount of work as walking for eight hours. You can’t take those things for granted. Even the little things you may not notice, like a new neighbor or pasturemate, might mean needing to change a horse’s diet.”