Shannon Pratt Phillips, M.S., Ph.D., PAS, DPL-ACAS Nutrition, Professor of Animal Science, Equine Nutrition and Physiology, North Carolina State University, explains that forages include long-stemmed plant material such as pasture and hay, as well as haylage, hay cubes, chopped hay and more. “Forages are the most important part of a horse’s diet because they provide the bulk of necessary nutrition,” she said.

“It takes horses awhile to eat the long-stemmed plant material in hay, pasture or haylage, which is good for their well-being and behavior; they don’t get as bored,” said Phillips. Since forage takes time for horses to consume, she notes that it also aids in saliva production. “Saliva contains bicarbonate, which can potentially counteract acidity in the stomach. If a horse has issues with ulcers, forage can be very helpful,” she added.

After passing through the stomach, forage moves into the large intestines and colon, keeping them healthy and functioning properly. “Forage, or roughage, keeps things moving in the gut,” Phillips said. “If horses don’t get enough forage, they are more prone to colic, ulcers and other digestive problems.” 

Forage is broken down into two basic types—grasses and legumes. Grasses include orchardgrass, timothy, bluegrass, Bermudagrass and fescue, while legumes are primarily clover and alfalfa. “Clover is beneficial in a pasture, whereas alfalfa is usually better for horses when cut and fed as hay,” said Phillips.

Legumes generally have more protein and calcium than grasses. “Most sporthorses don’t need 100% alfalfa because it contains too much protein and calcium,” Phillips noted. Excess protein takes more energy for a horse to break it down, while too much calcium disrupts the calcium-phosphorus balance in the diet. “Feeding a mix might be more appropriate, depending on the horse, but a good-quality grass hay will usually do fine,” she added.

The nutritional value of hay depends largely on the plant species and their maturity. “If hay is cut when immature and still growing, it will have higher nutritional density than older, more mature and stemmy hay,” said Phillips. “Examine your hay to identify the plants and assess how mature they are—with immature hay being green with more leaves—and what the seed heads look like in mature hay.” You can tell if alfalfa has bloomed and is more mature if you see small purple flowers—or if it’s even older and the blooms have turned to seeds. With timothy, you can see the long seed heads.

While a plant’s maturity can give you some insight, hay analysis allows you to take a closer look into its nutritional value. “It’s impossible to know how much protein or calories are in hay just by looking at it, even if you know its 60% alfalfa and 40% timothy,” Phillips said. “The only way to really know is to get it analyzed.” 

Feeding Forage to Sporthorses

Brian Nielsen, Ph.D., PAS, DPL-ACAN, Professor of Equine Exercise Physiology at Michigan State University and an equine nutritionist who owns racehorses, explains that sporthorses are frequently kept in stalls rather than on pasture, limiting their access to nutrients in fresh grass. “We provide hay because they can’t be out on pasture,” he said. “Ideally, you want to provide as many of the necessary nutrients as possible from forage.”

People often assume elite athletes like sporthorses need high-grain diets. While Nielsen says there may be some truth to that, depending on the individual horse, he still emphasizes the importance of forage and notes that many sporthorses do very well on high-forage diets.“Some people think you can’t meet all of a horse’s caloric requirements from pasture,” he said. “But often you can if it is lush, green pasture.”

Nielsen notes a 2017 Swedish University of Agricultural Sciences study found that a forage-only diet in 2- and 3-year-old Standardbreds didn’t negatively affect their ability to qualify and race before the age of 4. Also, an Australian nutritionist has begun similar work with Thoroughbred racehorses, finding promising results with high-forage diets opposed to high-grain diets.

During a presentation at the 2025 European Equine Health and Nutrition Congress in the Netherlands, Nielsen learned that it’s beneficial when more acetate is produced during digestion, as a horse digests forages in the hindgut. The more acetate produced, the more metabolic acidosis (or too much acid in the body) is delayed. “On a high-forage diet, a horse produces more acetate,” he explained. “Delaying metabolic acidosis could improve performance by delaying the onset of fatigue.”

A high-forage diet is important for sporthorses, and green pasture is often a good choice compared to hay that’s been stored or is low in nutrients. But Nielsen notes that green pasture is very high in some soluble carbohydrates. “It might not be good for horses with metabolic problems, but can be wonderful for sporthorses because it provides the energy they need,” he said. “Horses in the Swedish study were fed haylage, which is full of soluble carbohydrates compared with hay that’s been dried and stored. The horses in Australia were fed good hay, with a high-nutrient content.”

Selecting Forage for a Sporthorse’s Specific Needs 

It is important to select the right kind of forage for the individual. For sporthorses, it must provide adequate energy and contain a reasonable amount of protein. “Horses don’t actually have a requirement for protein. The National Research Council Nutrient Requirements of Horses guidelines give one, but what horses really need are amino acids—that make up the protein,” Nielsen said. “A certain feed might contain a lot of protein but if it is deficient in some of the limiting amino acids, the horse may not be able to utilize the protein.”

If your horse is on pasture, it will be difficult to determine exactly how much he’s eating, but you can tell if he’s maintaining proper weight, so keeping track of his body score is crucial. “Not every pasture is suitable to keep weight on and provide enough of the nutrient requirements for hardworking horses,” he said. “Even when horses are on good pasture, you may need to provide supplemental forage like hay. We can’t just assume everything will be fine if they have unlimited forage.”

Nielsen recommends feeding hay that contains some legumes, but this can depend on the forages available in your region. “If there’s some alfalfa in the hay, however, it will usually improve protein quality and provide plenty of calcium and most other minerals,” he said. “Many grass hays are also fine, but some are not. This is why it is important to have hay analyzed.”

Certain circumstances can sometimes prevent horse owners from obtaining their preferred hay. If your area is in severe drought or wildfires impact agricultural lands and hay crops are short, hay supplies may be scarce and very expensive. While hay alternatives are an option during those times, Nielsen suggests sticking with hay if possible. “Hay cubes may be recommended in times of drought or when you might have trouble finding affordable, good hay. This might sound reasonable on the surface, but do the math,” he advised. “Hay might be expensive, but if you price what it costs on a per-pound basis and compare it to the cost of hay cubes or other alternatives, you are generally better off to pay the high price for quality hay that your horse is familiar with and performs well on.”

Nielsen notes that hay cubes are an acceptable option for older horses with dental issues who are unable to chew hay. “But for a young, healthy sporthorse with good teeth, the hay may still be a better buy,” he said.

Changing Forages 

If you change forages, such as different cuttings of hay with different maturity or switch from hay to pasture, it’s important to gradually transition your horse to the new variety. “The microbial population in the hindgut can be disrupted if you make transitions too quickly,” Nielsen explained. He suggests the following plan for making a forage change:

Day 1: 25% new hay and 75% original hay
Day 2: 50% new hay and 50% original hay
Day 3: 75% new hay and 25% original hay 
Day 4: 100% new hay 

“Or you can even take a little more time to gradually switch,” Nielsen said. 

While it’s ideal to bring your own hay to horse shows, that may not always be possible. If you need to feed hay you purchase at a show, Phillips suggests mixing in hay products, such as chopped hay, to help reduce the variation in hay when traveling since the products are fairly similar bag to bag. “Bring as much of your own long-stemmed hay as you can, but it might be helpful to augment it at home or at shows with some chopped hay since it might be more consistent,” she said. Another suggestion from Phillips is to ask the show facility if they can provide a hay analysis so you can plan accordingly based on the hay that your horse eats at home and the hay available for purchase onsite. 

Your horse might do well on pasture, but if you suddenly take him off pasture and feed hay when you’re competing, this alters his diet significantly. “If you show often and your horse only gets pasture periodically while competing, you don’t want pasture to be the main component of the diet when he’s home, even though he’d be happier on pasture,” said Phillips.

In this situation, she recommends feeding hay to your horse in the barn and only offering him pasture as an extra treat. You also might consider using a grazing muzzle so he can still enjoy being turned out and eat quite a bit of grass without gorging himself. 

When Forage Isn’t Enough

It’s also important to consider what you supplement your horse’s hay with to ensure his diet is balanced. “If you have excellent quality hay and your horse is a hunter with lower energy requirements than a show jumper or eventer, you could potentially meet all of his calorie requirements with just excellent quality hay,” Phillips said. “It all depends on the hay quality.” While good hay can meet almost all of your horse’s nutrient requirements, he might need a vitamin supplement containing trace minerals and vitamins A and E, which tend to be higher in green pasture and lower in dry hay. If he needs additional protein, a ration balancer can provide those key vitamins and minerals, as well as protein. 

For horses with higher energy requirements, Phillips says feeding a concentrated energy mix is likely beneficial. “There are many thoughts about which types of concentrates are better for which horses. Some do better with higher amounts of fat, and others do better with higher amounts of sugar; it often depends on what the horse is doing,” she said. “Those decisions should be made based on what the forage provides.” 

Rather than going with a cookie-cutter feeding plan for your horse, Phillips suggests taking a more in-depth look. “I make a graph to see what the hay covers and see what gaps I need to fill as opposed to just deciding to feed four pounds of a certain feed every day and tossing some hay to that horse,” she said. 

Each horse is an individual and has different needs. One horse might lose weight on the same diet that another horse stays fit on and keeps ideal weight. It’s important to know your horse and monitor his body condition, fitness and overall well-being. If you think you need to make a change to your horse’s diet, work with your veterinarian or an equine nutritionist to discuss your concerns and set up your horse with a diet that is ideal for him. 

For More:

• Read more about selecting the right hay for your horse here.
• To learn more about proper nutrition for sporthorses, click here.

This article originally appeared in the summer 2025 issue of Practical Horseman.

Poll: What Is Your No.-1 Factor When Considering Supplements for Your Horse

This poll is sponsored by Cosequin®

One day there was a menacing blue manure bucket in the corner that Rio was sure contained a variety of monsters. Another time, two geese outside the arena got into a honking contest, and the gelding ran for the hills. Most offensive, however, was a lesson following a Halloween-themed show. The three straw bales and small scarecrows that comprised a jump were more than Rio could handle and resulted in a snorting, pawing bucking hissy fit.

To ensure there weren’t any underlying health issues going on, including his eyesight, Neth had her veterinarian out, who gave Rio a clean bill of health. Occasionally, she and her trainer tried giving him a calming paste, but didn’t see much of a difference, so after hearing about cannabidiol (CBD) products for horses, she decided to give it a try.

While the results weren’t instantaneous, Neth said within a few weeks, she did start to see a noticeable difference in her gelding. Every once in awhile, something out of the ordinary still startled him, but overall Rio seemed much happier and more chill about situations that would normally have set him off.

You’ve probably heard about the benefits of CBD for humans and dogs, but in recent years a number of companies have focused their research on CBD in horses. As a result, it’s gained popularity as an alternative or complementary treatment for a variety of equine issues, particularly those involving pain, inflammation and anxiety. Researchers, however, are still working to fully understand how CBD works in equines.

To help you determine whether a CBD-based product might be beneficial for your equine partner, we’ll explain how it affects horses’ physiology, the best modes of administration and the various types of products on the market.

Cannabis Connection: What Is CBD Exactly?

Holistic veterinarian Joyce Harman, DVM, a leading authority on equine acupuncture and alternative medicine, explains that CBD is derived from cannabis plants, a genus cultivated around the world for thousands of years. Archeological evidence suggests that cannabis plants, which originated in Asia, were used by humans as early as 2800 BCE.

There are two main species of cannabis, and many strains within those related species. Hemp-type cannabis includes varieties traditionally cultivated for their fiber (rope, twine, etc.), seeds (for food) and oils. Other types of cannabis, classified as marijuana strains, have been used for centuries for ritual, medicinal and recreational purposes.

The active ingredients in all these plants are chemicals called phytocannabinoids. The marijuana strains of cannabis plants are cultivated to produce high levels of tetrahydrocannabinol (THC), a psychoactive (mind-altering) phytocannabinoid. By contrast, the hemp strains, which contain cannabidiol (CBD), are not considered psychoactive. Studies in people and animals suggest that cannabidiol can relieve anxiety, reduce inflammation and provide pain relief. It’s also prescribed to treat some types of epilepsy.

“The difference between hemp and a marijuana plant is the amount of THC,” Harman said. “The plants we want for our animals are hemp plants. They have been selected and cultivated for high CBD and little to no THC.” 

After the 2018 Agriculture Improvement Act removed industrial hemp from the definition of marijuana in the Controlled Substances Act, hemp was legally separated from its psychoactive cousin and new uses of the plant became economically feasible. Nonetheless, regulations governing CBD are constantly changing, with states taking different approaches to the sale of CBD products, so be sure to stay up to date on your state and local laws.

Benefits of CBD for Horses

Calming Effects:

One of the primary claims made about CBD centers on its calming effects. But unlike the psychoactive “high” produced by THC in marijuana, CBD is believed to soothe stress or anxiety. “Many horse owners and veterinarians have seen positive responses with CBD in animals that have been through stressful periods,” Harman said. “It helps with mental equilibrium.”

CBD interacts with the body’s endocannabinoid system, which regulates many physiological functions, including appetite, mood, pain sensation and immune response. By binding to certain receptors in the endocannabinoid system, CBD can help modulate these functions.

“CBD doesn’t make horses ‘stoned’ like THC would. The brain is still functioning normally,” Harman explained. “The horse is calm but if there is cause to be alert, the horse is still capable of being alert.”

It’s important to note, however, that these calming effects have not been proven in clinical studies, but Harman believes horses are excellent candidates for CBD trial therapies because modern equine management practices tend to put horses at risk of chronic stress. As we know, horses are designed to roam and constantly graze, but unfortunately many horse owners don’t have that option. The United States Department of Agriculture estimates that 6,000 acres of the country’s open land are lost every day due to the increasing demand for urban and suburban development, which translates into real-world hardships for many equestrians and horse owners.

“Equine athletes are sometimes confined in small spaces, separated from their social groups and asked to do things that don’t come naturally to them,” Harman noted. “Many horses are on edge all the time. When we get on them, they spook at everything. CBD can help them stay calm and ‘forgive and forget.’”

Inflammation and Pain:

CBD also shows promise for treating chronic pain in horses. Harman says it may be beneficial for helping with laminitis, insulin resistance, musculoskeletal pain, skin disease, chronic ulcers, uveitis and even Lyme disease.

“Cannabinoids have action in both acute and chronic pain by modulating pain signals in the central and peripheral nervous systems and acting similarly to an anti-inflammatory,” Harman wrote in her 2020 Innovative Veterinary Care Journal article. “CBD can also act as an antioxidant and support immune function.”

While CBD is rarely the only treatment a horse receives, it may offer pain relief without the potential side effects of long-term use of conventional anti-inflammatory drugs like phenylbutazone (bute). CBD’s effectiveness against chronic pain has yet to be scientifically proven and it appears to vary greatly among individual horses. But Harman advocates trying CBD, particularly when traditional treatments have failed to alleviate pain.

Types of CBD for Horses

CBD products for horses are available in pellets, powders and oils. Powders and pellets can easily be distributed in your horse’s grain rations. For powders, Harman advises selecting a product that is 100% hemp with nothing else added; while pellets often contain alfalfa or added mold inhibitors.

CBD oils are extracted from the hemp plant and then mixed with an oil base. “Any type of safe, healthy oil is fine to dilute it in—usually hemp seed oil or MCT oil from coconuts—to get an amount you can measure in a dropper for feeding,” she said.

While some people claim that rubbing the CBD-infused oil into a horse’s gums is the fastest delivery method to get cannabidiol into his system, Harman says it’s often more practical to add CBD to his feed, especially as recent studies suggest that it’s better absorbed when administered with food.

CBD Dosage for Horses

The amount of CBD needed to achieve the desired effects in horses varies, as individuals responds differently to the compound. However, it’s always important to follow the specific manufacturers’ feeding directions.

Fortunately, Harman notes that CBD has a relatively solid safety record in many species and also seems to be well tolerated by horses in preliminary studies. “One thing we know about CBD is that the parts of the brain it works on will not be adversely affected by overdose,” she said.

Still, it’s wise to be cautious about giving your horse too much CBD. Research has shown that higher doses of CBD can change liver enzyme levels in people and animals—although this may not be a problem, according to recent studies. But again, be aware that there aren’t specific studies in horses.

Harman advises to establish the smallest effective amount of CBD for your horse and stick with that. “I recommend starting at about 25 milligrams for about a week or 10 days. If you aren’t seeing improvement in the condition you’re trying to help, then double the amount (50 milligrams) for a while,” she said. “If that’s still not working, you can go higher until you find the level that works in that particular horse. But it’s always best to follow the manufacturer’s instructions as the quality or concentration can vary considerably.”

When administering CBD to combat inflammation and discomfort, Harman says a large loading (initial) dose might be helpful. “You might start at 50 milligrams for a week and increase it if necessary—on up to 200, if need be, and stay there for a few weeks or a month,” she noted. “If the horse becomes sound and is no longer in pain, you could back down until you find a comfortable level.”

If maximum doses of different CBD products don’t produce the desired results in your horse, it’s time to look for other alternatives. Regardless of the hype, Harman stresses that CBD isn’t a cure-all, and it won’t help every horse.

Potential Downsides

The potential benefits of CBD are clear. But there are also possible downsides. One of those concern comes from the fact that rules and regulations governing CBD products are often unclear and still evolving. Although the Food and Drug Administration (FDA) has approved a CBD prescription medication for treatment of certain types of seizures, the agency has declined to issue rules for other CBD products.

“It’s not apparent how CBD products could meet safety standards for dietary supplements or food additives,” said FDA Principal Deputy Commissioner Dr. Janet Woodcock in a statement explaining the decision. “The use of CBD raises various safety concerns, especially with long-term use. Studies have shown the potential for harm to the liver, interactions with certain medications and possible harm to the male reproductive system. CBD exposure is also concerning when it comes to certain vulnerable populations such as children and those who are pregnant.”

The FDA is calling on Congress to establish a regulatory structure to ensure the safety and efficacy of CBD products.

Regulatory Gaps

Until those regulatory gaps are bridged, Harman advises sticking with CBD products offered by well-established companies that are transparent about their ingredients and production standards. “When you see inexpensive CBD products, consider that there is often a reason they are so inexpensive,” she warned.

And especially if you compete with your horse, keep in mind that most equine sports’ organizations prohibit anything that might alter or enhance performance, including CBD. That means horses may be tested for CBD along with other prohibited substances.

To stay in compliance with competition rules, Harman suggests administering CBD between events. “We don’t know yet what a safe withholding time would be for all horses,” she noted. While it’s generally recommended to withdraw a horse from CBD seven days prior to competition, it can vary by individual.

Horses who compete less often, as well as those in rehab or on a break from competition, may benefit from CBD administered during down periods. “Then, if your horse is functioning in a calmer way, you may have improved the condition of his endocannabinoid system,” Harman said.

CBD Shopping Tips

As with any supplement, it’s best to purchase CBD supplements only from well-regarded manufacturers. “Reputable companies use organically grown hemp for their CBD products, but certification of organic status has only recently been granted to the hemp industry,” Harman pointed out. “Some products are grown responsibly, using organic methods, but are not certified as organic yet because the process is expensive and can take several years for a farm to obtain.”

Certificate of Analysis

A reputable company selling CBD products will also publish a certificate of analysis (COA) for each product on its website, verifying that it has paid to have these products tested. The COA lists everything in the product: the cannabinoids, any terpenes (other beneficial plant compounds), any solvent contamination, heavy metals, other chemical residues and microbiology—as well as any molds or bacteria.

It’s also smart to consider how a product was processed. “CBD can be safely extracted using carbon dioxide (CO2) or high-quality, organic ethanol,” Harman explained. “The cheap way is to use nasty chemicals like benzene. Your local gas station or convenience store might sell CBD, but you may be getting other chemicals along with it.” The COA will tell you whether there are residues left over from processing and whether the plants were grown in soils free of heavy metals or other contaminants. It will also tell you the strength (actual amount) of CBD in  the product.

THC Content

In addition, you want to verify that the product contains little to no THC, which can occasionally be present in trace amounts. The legal amount of THC to be in a CBD product is 0.3% and that amount will have no psychoactive effect. While Harman says that THC might be helpful in horses with cancer, dogs are highly sensitive to it, and researchers don’t know enough about THC to recommend its use in otherwise healthy horses.

For More:

SmartPak Equine commissioned a study on the safe use of their CBD ingredient at Louisiana State University School of Veterinary Medicine that was published in the Journal of Equine Veterinary Science, a  peer-reviewed scientific journal. You can read more about it, here. 

About Joyce Harman, DVM

Joyce Harman, DVM, has more than 30 years of experience in holistic veterinary medicine. She is the founder and owner of Harmany Equine Clinic in Flint Hill, Virginia. After receiving her veterinary degree from the Virginia-Maryland Regional College of Veterinary Medicine in 1984, Harman decided to explore alternative approaches to animal health. Over the years, she has incorporated a variety of holistic modalities into her practice, including acupuncture, herbal medicine, homeopathy, CBD and chiropractic care. Her website contains educational material, and she is currently working on an online nutrition and holistic health course. Harman is the author of The Horse’s Pain-Free Back and Saddle-Fit Book and is a sought-after speaker on veterinary topics around the world.

California ranch owner Bob Manns’s horse, Magic, was the oldest registered Arabian horse in the U.S. She remained healthy and sound throughout her 51 years and went on an hour-and-a-half trail ride just a month before she died peacefully in 2020. 

Horses have lived and thrived well into old age for centuries, but now there are more aged equines who are healthier and more active than ever before. Conversations with your veterinarian will help identify the particular issues and challenges your older horse is facing, and routine yearly blood work screening, consistent dental care, nutritional management and attention to joint health are key to his longevity.

Horses and Owners Aging Together     

There is increasing evidence that older horses are becoming a more significant part of the equine industry. A 2001 study published in the Journal of the American Veterinary Medical Association showed that the number of geriatric horses (older than 20) went from 2.2% of total equine patients in 1989 to 12.5% in 1999, while a 2015 National Animal Health Monitoring System equine study showed that the number of aged horses continued to double from 1998 to 2015. These increases are likely due to a number of factors.

There has been a rise in specialized veterinary services for older horses, which specifically address the common problems and needs of geriatric equines. Additionally, there has been a change in perception as to what older horses can still do with proper fitness and an increase in owner willingness to seek out and finance services to keep them going longer. 

This perception shift has likely been influenced by the increasing viability and longevity of the human population. And many equestrians, who are staying healthier and more active at older ages, want to help their equine companions keep pace. The United States Dressage Federation offers a Master’s Challenge Award for riders over 60, and in the ultimate acknowledgement of both aging human and horse athletic capabilities, The Dressage Foundation’s Century Club recognizes any horse-and-rider pair who completes a dressage test, at any level, with a combined age of 100 or more. 

In a 2011 research article titled “Welfare of Aged Horses,” Catherine McGowan, a researcher at the Institute of Aging and Chronic Disease and professor of equine internal medicine at the University of Liverpool England writes, “In the past few decades, the role of the horse as a companion animal has become more apparent.” She goes on to discuss a survey of 47,000 horse owners across the U.S. that showed 38.4% considered their horse to be a family member and over half (56.5%) considered them a pet or companion. This explains the drastically intensified care and attention that owners have given their horses, resulting in healthier, more athletic animals throughout their golden years.

Wellness Care to Keep Older Horses Vibrant    

The equine “fountain of youth” starts with better health in general. And paying close attention to seemingly simple details in older horses is crucial because small problems often have a ripple effect in seniors. Veterinarians are increasingly focused on their older patients and can more rapidly identify and treat problems and conditions affecting them than in previous decades. The basics are still very important. Vaccination programs help keep all horses protected from most common diseases, but it’s even more crucial for older (and younger) horses because they generally have weaker immune systems and can be more seriously affected by diseases. Consistent deworming with quality, targeted products has drastically reduced parasite damage in horses’ intestines, and with the reduced absorptive capabilities of some senior equines, more accurate deworming helps older horses maintain weight and reduces stress on their immune systems. 

Routine blood work screening has also enabled veterinarians to identify certain conditions in senior horses and initiate more effective treatments much earlier. Older horses are sometimes anemic, and a complete blood count (CBC) will identify such a problem. Veterinarians can then look for the cause of blood cell loss or reduced red cell production, which can range from low-level liver dysfunction to age-related bone marrow dysfunction, and initiate a treatment plan. In some cases, something as simple as adding a “blood builder” tonic or other specific supplement to an older horse’s diet can improve the red blood cell and hemoglobin levels. 

This improved oxygen-carrying capacity in the blood can provide senior horses with more energy, which leads to more activity and helps build and maintain muscle mass—something that is so important in older horses. More activity often leads to increased grazing, which helps address dietary concerns and weight management, and older horses with more energy tend to interact more with herdmates. Social interaction for senior horses is often overlooked but has proven important for reducing stress, boosting immunity and contributing to the quality of life for older equines. 

Blood work screening can also identify problems with liver, kidney, cardiac, and many other organ systems to help veterinarians and owners determine if any dietary, exercise or treatment changes are necessary. This can often add functional years to a horse’s life.

Addressing Dental and Metabolic Issues

Equine dental care has improved greatly in recent years. Dental problems are a major concern in older horses who often suffer from tooth loss, uneven wear patterns, sharp points, worn-down teeth and other dental diseases. Equine odontoclastic tooth resorption and hypercementosis (EOTRH) is a disease seen in horses generally older than 15. While it has likely been around for many years, the increased care and attention given to older horses, especially dental care, has caused the condition to be more widely recognized in recent years. EOTRH causes tooth damage and resorption which can lead to infection, abscesses and dental fractures. Older horses with EOTRH or other dental problems can show signs of weight loss, difficulty eating and associated performance and behavioral issues stemming from constant pain and decreases in food intake. 

Older horses are also much more likely to experience metabolic problems, but increased use of early blood screening tests is helping to identify these conditions and provide earlier care. Pituitary pars intermedia dysfunction (PPID, formerly known as Cushing’s disease) affects a large percentage of older horses (20% or more in some studies). Common symptoms include a long, curly coat and muscle loss, but early signs of PPID and other metabolic problems (insulin resistance or equine metabolic syndrome) can be harder to spot. Long-term weight and muscle loss; lack of energy; depression; susceptibility to skin infections, hoof abscesses, laminitis and other problems brought on by poor glucose regulation and a stressed immune system were often thought to be inherent consequences of old age. But through early detection, veterinarians can provide these horses with pharmaceutical treatments, exercise programs and dietary changes to help slow the progression of metabolic problems and remain healthier and more active.

Feeding the Older Horse

As veterinarians identify more dietary-related problems in senior horses, such as obesity, laminitis, PPID and other metabolic concerns, gastrointestinal irregularities and arthritis, the equine nutrition industry has developed new feeds with targeted ingredients and feeding strategies to help manage these conditions.

A variety of new feed types, including pellets, cubes and chopped hay products, are also now available for older horses with poor dental conditions who might have a reduced ability to digest forage, which can lead to a host of other medical issues from choke to weight and muscle loss. 

Concern for aged equines has created an entirely new market for supplements designed to rebalance the bacterial environment of the older horse’s gut. These prebiotic and probiotic products promote healthy gut bacteria, which can help reduce loose stool and excessive gas, allow for better digestion and absorption and ultimately promote more stable weight and muscle mass in older horses. 

New research on protein, carbohydrate and other nutrient requirements of seniors—and the feeds developed based on this research—are providing older horses with more energy, which in turn enables them to be more active and functional athletes as they age.

A report from the University of Tennessee Institute of Agriculture concludes that “nutrition for geriatrics, or old[er] horses with age-related diseases, has become more prevalent because horses are living longer and more data is available on nutrition risk factors for diseases and digestive disorders. We now have a much better under standing of how to manage the special needs horse.”

Healthy Joints for an Active Horse     

Optimizing joint function and reducing symptoms associated with osteoarthritis is another major area of veterinary research and product development that has extended the athletic capabilities and lifespans of older horses. As all animals age, they develop wear and tear injuries to their joints. This long-term joint stress eventually leads to osteoarthritis that can be career-ending, crippling and sometimes even life-threatening. Anything that reduces a horse’s mobility will affect his ability to graze, which can result in weight and muscle mass loss. Additionally, pasture grass provides horses with needed essential nutrients such as Vitamins A and E, omega-3 fatty acids, and minerals like calcium, phosphorus, copper, iron, magnesium, potassium and selenium. Horses who don’t graze enough and consume decreased amounts of these nutrients are less healthy and more susceptible to disease. 

Also, when horses cannot move around freely, they lose that important ability to interact with their herdmates, which can lead to isolation, depression and physiologic stress. 

The majority of drugs previously available for arthritis pain control, such as phenylbutazone (Bute) and Banamine^®, can cause stomach ulcers and intestinal issues as well as kidney damage with long-term use. However, new, pain-relieving medications, such as firocoxib, have been a major factor in increasing equine longevity, as they’re not as harmful to a horse’s intestines and organ systems and can be used for long periods of time. Long-term pain management enables some older horses to continue competing at lower levels while keeping others pasture-sound for much longer than previously possible. 

Glycosaminoglycans, hyaluronates, chondroitin-based products and any number of osteo-protective substances have been proven to slow the progression of arthritis. This class of medications works by promoting healthy joints and cartilage while also slowing joint deterioration and extending the functional life of older joints. The common use of these products at earlier ages is creating a population of older horses with joints that are in much better condition than similarly aged horses in past decades. 

The more recent development and use of regenerative medicine products such as stem cells, platelet-rich plasma (PRP), interleukin-1 receptor antagonist protein (IRAP), Pro-Stride^® and numerous other intra-articular joint injections has also greatly enhanced veterinarians’ abilities to treat early joint issues and maintain better joint function as horses age. With improved joint health, continued exercise is not only possible for older horses but is essential to keeping them engaged and functional.

Overall, horses are definitely living longer and better lives. The key to helping older horses get the most out of their golden years is to consider each as an individual. Not all older horses are the same, and age, after all, is just a number. Specific decisions and treatments tailored for each older horse can be determined with the help of your veterinarian. But not seeing your horse as simply “old” is the first step. Continuing to train, exercise, compete and enjoy your senior equine partner, as much as is possible, is the ultimate way to grow older and better together.

Age: What’s in a Number?

Traditionally, the veterinary community has considered horses 20 and over as “aged” or “senior” when considering their nutrition, joint care, reproductive considerations and management. But this classification system is largely arbitrary, with the 20-year mark decided upon with little research. Recent work by the National Research Council and others suggests that there may be better ways to define “old age,” which can help veterinarians provide more specifically targeted ways to care for aging horses. Researchers have suggested that equine age be defined by a combination of three factors: physiologic age, chronologic age and demographic age. 

Physiologic age refers to the internal factors of the animal—natural decreases in reproductive performance; decreases in tendon, ligament and joint function; decreased muscle mass and reduced capabilities in digestive, liver, kidney, cardiac and other organ systems. The generally accepted age for an “older” horse, from a physiological age perspective, is from 15 to 20. A reining horse who has been extensively competed as a young horse and experienced a reduction in his musculoskeletal system health may be considered “old” at 10, while a lightly used trail horse may be functionally sound and healthy and not “physiologically old” at 25.

Chronologic age refers to the number of years from birth compared to expected longevity. There are horses that live to be 40—and some well beyond that—and the number of these “seniors” is growing. Using this criterion, horses are classified as “old” when they’re between 20 and 30 and “very old” if over 30. As more horses continue to live longer, you can expect these chronologic age classes to be periodically revised.  

Demographic age is determined by survival relative to a specific subset of a population defined by a region, discipline or other factors, including economics, use or social issues. The age at which an individual becomes “demographically old” is the age at which they are older than 75% of the other members of that specific group. Horses living in harsh climates generally may not live as long as horses in milder weather locations. Some areas view horses differently from a societal perspective, which often determines the level of care that they are given, and some horse-owning populations have differing economic concerns, which can affect horse care, health and, ultimately, longevity.

A 15-year-old horse living in generally harsh conditions in northern Sweden may be seen as a “senior” relative to the majority of other horses living there. Racehorses are generally put under more stress at an early age and have higher incidences of injuries associated with their use, so as a demographic group, they may not live as long as horses in other disciplines, such as dressage or endurance. Therefore, classifying an off-the-track Thoroughbred as “old” at 18 may be more correct than applying that same label to an 18-year-old dressage horse. Demographic age considers all these different factors and can help make discussions about equine aging much more productive. 

The bottom line is that age, for all of us, is so much more than just a number. Using a combination of all these age criteria for each individual may be a better way at arriving at a horse’s more accurate and functional “age,” which can then determine management and maintenance programs for these equine seniors.

About Kenneth L. Marcella, DVM

Kenneth L. Marcella, DVM, is a graduate of the New York State College of Veterinary Medicine at Cornell University. For more than 30 years, he has treated sporthorses of all disciplines and levels, including international competitors. Dr. Marcella has served as a veterinary official at many events around the world, including national championships, world championships and Olympic competitions. He is board-certified in thermal imaging and is currently a member of the board of directors of the American Academy of Thermology. With an undergraduate degree in English from Dartmouth College, Dr. Marcella has also written articles for numerous publications. 

But after keeping him on a strict diet and trying to get him back in shape with plenty of exercise, he hasn’t shed any weight and still has noticeable fat deposits on the crest of his neck and tail head. Once your veterinarian takes some blood samples, she diagnoses your equine partner with Equine Metabolic Syndrome (EMS).

While you may be concerned, EMS is more common than you might think, and by working closely with your veterinarian and making some key changes to your horse’s lifestyle, you can get him back to a healthy weight to ensure he stays healthy for years to come and is able to perform his best.

What Exactly is EMS?

EMS is a disorder characterized by insulin dysregulation, or the inability to metabolize carbohydrates and regulate blood insulin levels correctly. (In the past, the clinical signs of this disorder have been known as hypothyroidism, pre-laminitic syndrome, peripheral Cushing’s disease, or “syndrome X.”)

As you might recall from biology class, insulin isa hormone secreted by the pancreas after a meal. It is released into the bloodstream after carbohydrates are broken down into glucose during digestion, causing the blood glucose (blood sugar) levels to rise.

One of insulin’s primary functions is to enable the transfer of that glucose from the blood into the body’s cells, where it is used to create energy. Once that transfer occurs, the blood glucose levels drop back down, and insulin’s job is done until the next meal.

Unless, that is, something goes wrong in the regulation process. In what is called insulin resistance, the fat deposits in affected horses release hormones that adversely affect the ability of the body’s tissues to respond normally to insulin. This causes a buildup of excess glucose in the blood and prompts the release of more and more insulin, often overwhelming the pancreas.

In humans, this kind of abnormal response can lead to type 2 diabetes. In horses, the result is what we now call Equine Metabolic Syndrome.

1. Breed, Environment and Other Factors Affecting EMS Susceptibility

Several genetic, environmental and physiological factors can contribute to EMS. Some breeds or types of horses are inherently prone to this disorder. These include Arabians, Morgans, Paso Finos, Saddlebreds and warmbloods. Donkeys and ponies are also at high risk. However, any “easy keeper” that becomes obese on very little feed can develop EMS. The classic trigger is a diet high in sugar—too much grain or forage high in nonstructural carbohydrates (NSCs). This, combined with a lack of regular exercise, can set the stage for EMS. The condition generally appears between the ages of 5 and 15 years.

As you’ve no doubt guessed, typical signs of EMS include increased appetite, excessive weight that can’t be lost and those characteristic fat deposits (although not every EMS horse is fat). Repeat instances of laminitis and other metabolic issues—occasionally at the same time—are other possible clues that your horse has EMS. So is an unusual amount of fatigue. If your horse is a breeding animal, infertility can be another sign.

2. Importance of Prompt Diagnosis

Early diagnosis of EMS is essential for the best possible outcome. So, if your horse is an “easy keeper” and overweight despite your best efforts to keep him trim—or if he has unusual fatty deposits or a nagging, unexplained lameness in a forelimb—it’s wise to get him professionally evaluated for this disorder.

Your veterinarian may screen for EMS by measuring blood insulin and glucose concentrations from samples taken first thing in the morning, after your horse has been fasted for six to eight hours. This is the best way to diagnose moderate to severe cases of insulin dysregulation.

Dynamic Tests: Dynamic tests that assess the body’s responses to a “glucose challenge” may be necessary to diagnose EMS in horses whose metabolic signs are not yet pronounced enough to detect the usual way. In one of these challenges, the Oral Sugar Test (OST), the horse is fasted for three to 12 hours and then given an oral dose of corn syrup. Blood samples are collected prior to and 60 to 90 minutes after corn syrup administration. The blood samples are tested for insulin to determine the horse’s response to a large increase in blood glucose concentration. EMS horses will demonstrate a large spike in blood insulin levels after corn syrup administration, while normal horses will not exhibit a pronounced spike in blood insulin concentration.

An insulin tolerance test (ITT) can also be performed to measure the ability of your horse’s tissues to take up glucose (insulin sensitivity). This involves comparing the glucose concentration of a baseline blood sample to that of a sample taken half an hour after a dose of insulin is administered.

Rule out PPID: When screening an older horse it’s important to rule out an age-related endocrine disorder called Pituitary Pars Intermedia Dysfunction (PPID, or equine Cushing’s disease). Unfortunately, the two can coexist, with PPID believed to worsen insulin dysregulation in horses also affected by EMS.

3. Treatment Options and They Can Help

Treatment of EMS is important, even if your horse is more “pasture ornament” than athlete. Why? Left untreated, this disorder can lead to painful complications. One of the most serious of these is laminitis, which can be crippling and even fatal.

For individuals who are “easy keepers” and obese (as most EMS horses are), simple changes in management can encourage weight loss. This should improve insulin sensitivity and help control the disorder.

But here’s the thing: Merely cutting your horse’s rations may not be enough. It is the restriction of carbohydrates that is critical to decreasing his body’s glycemic and insulinemic responses. Even if your horse consumes only forage, limiting his grazing is especially important in the early spring and autumn, as well as in the afternoon, when pasture grass is richest in natural sugars. (Grazing muzzle to the rescue!)

Hay can be an issue, too; consult your veterinarian about the most appropriate types to feed and consider having each load tested for NSC content. Ration balancers or complete feeds designed for horses with insulin dysregulation may also be useful.

If these dietary tweaks aren’t enough to reduce your horse’s weight, additional exercise may be prescribed.

Finally, if management changes don’t work, your veterinarian might suggest medical therapy with drugs like thyroxine or metformin to help stimulate weight loss and regulate insulin responses. Your veterinarian may also recommend that you add a metabolic supplement to your horse’s regimen.

4. Preventive Measures

To help prevent EMS—particularly in those high-risk, “thrifty” breeds—it’s best to feed using an ideal body condition score as your guide rather than just “eyeballing it.”

Keep in mind, too, that horses who are predisposed to this disorder will always need low-carbohydrate hay or pasture grass. That means their hay should ideally be tested for NSC levels. Their access to pasture should also be limited during periods of high sugar content (early spring and autumn), with early morning grazing preferred.

And don’t forget regular exercise! It’s just as important for horses as it is for humans.

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— Melissa F., New York

A: Vitamin E is a critical component of the equine diet as a potent antioxidant with roles in combatting oxidative stress, supporting the neuromuscular system and enhancing immune system responsiveness. The daily requirement for horses can vary significantly based on weight, diet, workload and life stage. For reference, an 1,100-pound horse at maintenance should consume approximately 500 IU of vitamin E per day. That same horse’s requirement increases to over 1,000 IU per day if he’s in some type of exercise program.

Green pasture is the best and most abundant source of vitamin E. A horse with access to adequate pasture (quality pasture for approximately 12 hours per day) will naturally maintain a serum vitamin E level of 3-6 µg/ml (which is ideal). Hay is another story since the nutrient is rapidly depleted post-baling. It’s safe to assume that horses not receiving adequate pasture intake will need to rely almost entirely on what’s in their feed and/or supplements.

When to Test

It’s highly recommended that horses who receive little or no pasture are tested annually for serum vitamin E status. This is also a good practice as vitamin E is a sensitive compound and not always particularly stable in supplements and/or feed. While most feed and supplement companies do a great job offering a stable form of the nutrient, I’ve come across many cases of horses receiving far beyond their requirements yet still testing as deficient in my consulting practice. Thus, it’s important to make sure the dietary source of the nutrient is viable, and this can be achieved through a simple blood draw from your veterinarian.

For horses on quality pasture who also receive adequate dietary intake of vitamin E from their grain ration or supplements, regular testing is not as critical unless there are observed symptoms associated with deficiency or if you’re curious. It’s also important to note that horses receiving the exact same diets can have some individual variation in vitamin E metabolism. Thus, it is best to test the full herd if there is suspicion of deficiency.

Interpreting Test Results

When you receive your horse’s test results, it’s important to know how to interpret their serum value. Adequate serum concentration is ≥ 2 µg/mL (micrograms per milliliter). While 1.5-2 µg/mL is considered marginal, and < 1.5 µg/mL is deficient. A horse that scores ≤ 2 µg/mL should undergo a vitamin E supplementation protocol to return serum levels to ideal. It’s best to consult with your veterinarian or an equine nutritionist to determine the most appropriate product and amount to supplement. Because horses on abundant pasture will naturally maintain serum at 3-6 µg/mL, this is a great target for “ideal.”

Vitamin E test results can be confusing for owners as the scale goes up to 10 µg/mL (or 1000 µg/dL depending on the lab your veterinarian sends the sample to). Many owners believe their horses should be on the high end of the scale for best results in performance, health, etc. Based on the current data available, there isn’t a reason to believe that “high normal” (7-10 µg/mL) is better than the suggested 3-6 µg/mL range for serum.

Thus, if your horse doesn’t come back with a “high normal” value but is still within 3-6, there isn’t support for additional vitamin E supplementation. If you have further questions and want to know the ideal form or product for your horse, your best bet is to connect with your veterinarian or a nutritionist.

About Rachel Mottet, MS, PhD

Rachel Mottet, MS, PhD, is an independent equine nutritionist under her business Legacy Equine Nutrition. She earned her B.S. in Equine Science from the University of Wisconsin River Falls, her M.S. in Animal Science from North Dakota State University and her PhD in Nutrition and Animal Science from the University of Minnesota.

Professionally, Mottet has worked with horse owners all over the world as an invited lecturer, university professor and consulting equine specialist for numerous equine feed and supplement companies. She has worked with FEI and Olympic competitors in numerous disciplines and has successfully formulated diets for thousands of horses. She actively competes in hunter/jumpers and owns a farm outside of Ocala, Florida, where she lives with her two dogs and three horses.

For More on Vitamin E and Equine Health:

• Learn about vitamin E’s essential role in supporting your horse’s immune health here.
• Does your horse need vitamin E supplementation during the winter? Find out more here.
• A veterinarian explains the differences between natural and synthetic vitamin E and how to determine which is best for your horse here.

— Betsy H., New Mexico

A: Vitamin E can be a confusing nutrient for many horse owners due to its various forms, multi-faceted health benefits and because individual horses metabolize the nutrient at different rates. For a quick refresher on the basics, vitamin E is an antioxidant that plays a crucial role in maintaining equine health, particularly in supporting the immune system. It does this by protecting immune cells from oxidative stress, boosting antibody production and reducing inflammation.

A proactive approach to vitamin E nutrition can make a significant difference in a horse’s ability to resist disease, recover from injury and maintain optimal health and can be especially beneficial for those under stress or recovering from illness.

Like vitamins A, D and K, vitamin E is fat-soluble meaning that horses cannot synthesize it on their own, and it must be obtained from their diet, primarily through fresh forage. Therefore, when access to quality pasture is limited, ensuring adequate intake through diet or supplementation is a priority for horse owners, trainers and veterinarians alike, especially considering its profound impact on the immune system, muscle function and overall vitality of the horse.

Forms of Vitamin E

Whether you opt to give your horse a powder, pellet or liquid vitamin E supplement, there are two primary forms of the nutrient: natural and synthetic.

Natural vitamin E is listed on an ingredient or feed label as “d-alpha-tocopherol” or the tocotrienols, without the “l.” This is the most bioavailable form of the nutrient, meaning it is absorbed and utilized more efficiently by the horse’s body. Natural vitamin E supplements are often recommended for horses with higher needs, such as those in intense training or those recovering from illness.

Synthetic vitamin E will be listed as “dl-alpha-tocopherol,” or some variation starting with a “dl.” While this form is more commonly found in feeds and supplements, it is less bioavailable than the natural form (it’s not absorbed or utilized as efficiently as natural forms). However, it can still provide adequate levels of the nutrient when administered in higher doses.

There are also differences in how the horse’s body absorbs the two forms. Natural vitamin E seems to bind better to specific transport proteins in the liver, which enables the nutrient to be delivered to other tissues. Synthetic forms are excreted faster than natural ones, and therefore don’t have as much time to reach the tissues where they are needed. In other words, a horse must consume more of the synthetic form to achieve the same levels in the bloodstream as the natural form.

Is Natural or Synthetic Vitamin E ‘Better’?

There’s been much debate regarding whether to supplement with natural or synthetic products, and many people swear by one or the other. Some research has suggested that natural vitamin E outperforms synthetic forms when it comes to minimizing oxidative and muscle cell damage in exercising horses. While powdered synthetic vitamin E is typically a mixture of vitamin isomers, some of which are more bioavailable than others.

Synthetic vitamin E is often added to many horse feeds and supplements because it’s less expensive. Natural products are usually about twice that of a synthetic product. Either way, you will get about the same effect at a similar cost.

With either form, absorption can be improved by adding fat to your horse’s grain ration. Fat binds with vitamin E and helps carry it across the intestinal wall and into the bloodstream. Researchers have also explored other methods to improve absorption. Some products contain “micellized” vitamin E, which means it has been chemically changed to improve absorption. Another approach is called nanodispersion, which separates the nutrient into tiny droplets that disperse across a wider range of the intestinal wall. Both methods have been shown to aid absorption.

Takeaway

To ensure horses receive enough vitamin E, owners and caretakers must pay close attention to their diets. Fresh pasture is the best natural source rich in the nutrient. However, horses that are on restricted grazing or those that primarily consume hay may require supplementation.

The National Research Council recommends that horses consume 1-2 international units (IU) per kilogram body weight of vitamin E daily. This equates to 500-1,000 IU for a 1,100-pound horse. Higher levels may be recommended for horses in hard work or those with certain health issues.

Due to the many variables that affect individual vitamin E levels in horses, establishing a baseline blood vitamin E level is important to determine whether your horse is deficient. If he is, work with your veterinarian to determine the appropriate supplement for him and to recheck his levels after supplementation to ensure they’re not too low or too high. From there, your veterinarian can advise you on making any necessary adjustments to his supplement dosage.

About Tania Cubitt, PhD

A native of Queensland, Australia, Tania Cubitt, PhD, received a bachelor of science in animal science at the University of Queensland before receiving her master of science degree in equine nutrition and growth at Virginia Tech University. She went on to receive her doctor of philosophy degree in equine nutrition and reproduction also at Virginia Tech. Cubitt currently works as an equine nutrition consultant at Performance Horse Nutrition and focuses on developing feeding strategies for horses with special needs.

For More:

• Learn how vitamin E can help support your horse’s immune system here.
• To help determine if your horse needs supplementation throughout the winter, click here.

— Kathy P., Pennsylvania

A: Vitamin E is a fat-soluble antioxidant that plays a crucial role in supporting horses’ immune systems and other physiological processes. In its most active form, alpha-tocopherol, vitamin E is most potent as an antioxidant and serves to protect immune cells from oxidative stress, boost antibody production and reduce inflammation.

Oxidative stress arises when free radicals (unstable molecules generated through metabolism or environmental factors) accumulate and cause cellular damage. Vitamin E helps neutralize these free radicals, preventing the destruction of cell membranes and other essential cell structures.

Horses cannot synthesize vitamin E on their own, and therefore must obtain it from their diet, primarily through fresh forage. Ensuring adequate vitamin E intake through diet or supplementation is a priority for horse owners, especially considering its profound impact on the neuromuscular system.

Vitamin E deficiency often occurs when horses have limited access to fresh pasture, as dried forages like hay and processed feeds contain significantly lower levels of vitamin E. Primary clinical signs and conditions associated with vitamin E deficiency in horses include muscle loss, weakness, poor performance and, in some cases, neurologic disease.

Evaluating Your Horse’s Vitamin E Intake

Many variables need to be considered when evaluating your horse’s vitamin E intake. The amount of vitamin E provided by pasture grazing depends on factors such as location, season, plant species, soil type and the amount of time your horse spends on pasture.

It’s challenging to make even broad generalizations about what type of pasture and how much would provide adequate vitamin E for any given horse because there simply hasn’t been enough research into the amounts of vitamin E in different pasture types—and due to the variation in absorption rates between individual horses. So, for example, we can’t say that if your horse is on timothy pasture for X hours a day in the spring, then his vitamin E levels are probably OK. It’s best to have his vitamin E levels checked directly.

It’s also important to consider the amount of vitamin E your horse gets from his daily rations, including targeted supplements (You can find this information in the ingredients’ label.) Most equine feeds and ration balancers, however, contain synthetic vitamin E, which is not well absorbed in horses and therefore usually doesn’t provide adequate amounts of the vitamin.

The National Research Council recommends that horses consume 1-2 international units (IU) per kilogram body weight of vitamin E daily. This equates to 500-1,000 IU for a 1,100-pound horse. Higher levels may be recommended for horses in hard work or those with certain health issues.

When determining whether your horse needs vitamin E supplementation in the late fall and winter, it’s also important to keep in mind that horses store vitamin E in the liver and fat tissues. Depending on pasture access in the spring and summer months, they can rely on these stores for up to 18 months before problems related to dietary vitamin E deficiency may be observed. This is how wild horses maintain their vitamin E levels throughout the winter.

However, individual horses metabolize vitamin E at different rates, so the time they can go without consuming vitamin E can vary. Additionally, some horses are genetically predisposed to diseases caused by vitamin E deficiency such as equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy, a neurologic disorder that can cause ataxia (incoordination), dragging the feet and weakness.

Establish a Vitamin E Baseline

Due to the many variables that affect individual vitamin E levels in horses, establishing a baseline blood vitamin E level is important to determine whether your horse is deficient in vitamin E. If he is, work with your veterinarian to determine the appropriate supplement for him and to recheck his vitamin E levels after supplementation to ensure they’re not too low or too high. From there, your veterinarian can advise you on making any necessary adjustments to his supplement dosage.

The timing on when to recheck his levels depends on the type of vitamin E supplement he’s getting. Water-dispersible vitamin E products are highly bioavailable; therefore, it’s generally recommended to recheck within two weeks of starting. For powders and pellets with natural vitamin E, the bioavailability is lower, so it takes two to three months to increase levels.

Once a reasonable level is achieved, it’s always wise to recheck your horse’s levels once or twice a year. This is especially true if his diet changes significantly or if you notice any changes in his health that could be related to vitamin E levels, such as muscle loss, decreased performance, incoordination or weakness. On the other end of the spectrum, excessive vitamin E can cause health issues such as increased bleeding risk. Vitamin E interferes with vitamin K metabolism, which can increase the risk of bleeding.

Regardless of your horse’s situation, always consult with your veterinarian before making significant changes to vitamin E in your horse’s diet.

For More:

To learn how vitamin E can help support your performance horse’s immune health, click here.

About Carrie Finno, DVM, DACVIM, PhD

Carrie Finno, DVM, ACVIM, PhD, is an equine internist who serves as associate professor in veterinary genetics and the Gregory L. Ferraro Endowed Director of the Center for Equine Health at the University of California, Davis. She received her veterinary degree from the University of Minnesota in 2004 and then completed a three-year residency in large animal internal medicine at UC-Davis. She elected to pursue a career in translational genetic research, with a strong focus on inherited neuromuscular diseases. Her research studies the interaction of vitamin E and neural development in a naturally occurring disease in the horse.

— Lucy C., Michigan

A. Vitamin E, a fat-soluble antioxidant, plays a crucial role in maintaining the health of horses, particularly in supporting their immune systems. It’s an essential nutrient that horses cannot synthesize on their own, and it must be obtained from their diet, primarily through fresh forage.

Vitamin E plays supports the immune system of horses by protecting immune cells from oxidative stress, enhancing phagocytosis, boosting antibody production and reducing inflammation. Given its importance, ensuring adequate vitamin E intake through diet or supplementation in equine diets is a priority for owners, trainers and veterinarians alike, especially considering its profound impact on the immune system, muscle function and overall vitality of the horse.

A proactive approach to vitamin E nutrition can make a significant difference in a horse’s ability to resist disease, recover from injury and maintain optimal health and can be especially beneficial for those under stress or those recovering from illness.

The Role of Vitamin E in Horses

Vitamin E, primarily in its most active form, alpha-tocopherol, serves as a potent antioxidant. Its primary role is to protect cells from oxidative damage, which is particularly important in the muscles, nervous system and immune cells. Oxidative stress arises when free radicals, unstable molecules generated through metabolism or environmental factors, accumulate and cause cellular damage. Vitamin E neutralizes these free radicals, preventing the destruction of cell membranes and other essential cell structures.

Horses, being athletic animals with high metabolic rates, are particularly susceptible to oxidative stress, especially during periods of intense exercise, illness or injury. Therefore, vitamin E is crucial not only for protecting muscle and nerve tissues but also supporting immune function, which in turn helps with disease resistance and recovery.

Equine Immune System

The immune system is a horse’s primary defense against infections, diseases and other foreign invaders. It comprises two key components: the innate immune system (the body’s first line of defense) and the adaptive immune system (which involves more specific responses, including the production of antibodies).

Vitamin E plays a significant role in modulating both innate and adaptive immune responses. Here’s how it affects different components of the equine immune system:

1. Antioxidant Defense for Immune Cells: Immune cells are highly active and produce a large amount of free radicals during an immune response. Without adequate antioxidant protection, these cells can suffer from oxidative damage, reducing their ability to fight infections effectively. By neutralizing free radicals, vitamin E helps preserve the integrity of immune cells, enabling them to function optimally during an immune response.
2. Enhancement of Phagocytic Activity: Phagocytosis is a process where specialized immune cells, such as macrophages and neutrophils, engulf and destroy pathogens. Vitamin E enhances the efficiency of these cells, ensuring that invading bacteria, viruses and other harmful agents are rapidly neutralized. This boost to the innate immune system means that horses with adequate levels of vitamin E are more likely to fend off infections at an early stage.
3. Improvement in Antibody Production: Vitamin E is also involved in the adaptive immune response by influencing the production of antibodies, which are proteins that specifically target and neutralize pathogens. Studies have shown that vitamin E supplementation can lead to an increase in antibody titers (concentration) following vaccination or exposure to pathogens, which means that horses are better prepared to fight infections and are more responsive to vaccinations.
4. Reduction of Inflammation: Inflammation is a natural immune response to infection or injury, but chronic inflammation can lead to tissue damage and a weakened immune system. Vitamin E has anti-inflammatory properties, helping to regulate the inflammatory response and prevent excessive tissue damage. In horses, this can be particularly beneficial in reducing inflammation-related conditions such as arthritis or respiratory diseases.
5. Support During Stress and Illness: Horses undergoing stress, whether from training, transportation or illness, are at higher risk of immune suppression. Stress can increase the production of cortisol, a hormone that can suppress immune function. Adequate levels of vitamin E help mitigate the effects of stress on the immune system, ensuring that horses maintain their disease-fighting capabilities even during periods of physical or emotional strain.

Vitamin E Deficiency in Horses

Given the crucial role of vitamin E in the immune system and other physiological processes, a deficiency can lead to a variety of health issues in horses. Deficiency often occurs when horses have limited access to fresh pasture, as dried forages like hay and processed feeds contain significantly lower levels of vitamin E.

Some of the primary symptoms and conditions associated with vitamin E deficiency include:

• Weakened Immune System: Horses deficient in vitamin E are more susceptible to infections and may exhibit slower recovery times from illness or injury due to compromised immune function.
• Equine Motor Neuron Disease (EMND): This degenerative disease affects the muscles and nerves in horses and is strongly associated with vitamin E deficiency. EMND is a progressive condition that can lead to muscle wasting, weakness and eventually death if left untreated.
• Muscle Disorders: Without adequate vitamin E, horses can develop conditions like exertional rhabdomyolysis (tying-up), where muscles break down after exercise, causing pain and stiffness.
• Poor Coat and Skin Health: In some cases, a deficiency in vitamin E can manifest as poor coat quality or skin problems, as the vitamin is essential for maintaining healthy cell membranes.

Sources of Vitamin E for Horses

To ensure horses receive enough vitamin E, owners and caretakers must pay close attention to their diets. Fresh pasture is the best natural source of vitamin E, as green grass is rich in this nutrient. However, horses that are on restricted grazing or those that primarily consume hay may require supplementation.

There are two main forms of vitamin E supplements available for horses:

1. Natural Vitamin E (d-alpha-tocopherol): This is the most bioavailable form of vitamin E, meaning it is absorbed and utilized more efficiently by the horse’s body. Natural vitamin E supplements are often recommended for horses with higher needs, such as those in intense training or those recovering from illness.
2. Synthetic Vitamin E (dl-alpha-tocopherol): While synthetic vitamin E is more commonly found in feeds and supplements, it is less bioavailable than the natural form. However, it can still provide adequate vitamin E when administered in higher doses.

Supplementing Vitamin E for Optimal Immune Function

For horses that do not have access to fresh pasture year-round or those under heavy physical demand, vitamin E supplementation can be a critical part of maintaining a healthy immune system.

Supplementation is particularly important for:

• Performance Horses: Intense exercise generates more free radicals, increasing the need for antioxidants like vitamin E to prevent muscle damage and support immune function.
• Older Horses: Aging horses may experience a decline in immune function, and vitamin E can help support their immune response, reducing the risk of infections and illness.
• Horses with Chronic Conditions: Horses with conditions such as equine asthma or those recovering from surgery or illness may benefit from increased vitamin E to support healing and reduce inflammation.

About Tania Cubitt, PhD

A native of Queensland, Australia, Tania Cubitt, PhD, received a bachelor of science in animal science at the University of Queensland before receiving her master of science degree in equine nutrition and growth at Virginia Tech University. She went on to receive her doctor of philosophy degree in equine nutrition and reproduction also at Virginia Tech. Cubitt currently works as an equine nutrition consultant at Performance Horse Nutrition and focuses on developing feeding strategies for horses with special needs.

• Nickname: Socs
• Occupation: CCI4* and CCI5* Eventer
• Hometown: West Grove, Pennsylvania
• Basic Stats: 13-year-old off-track Thoroughbred gelding
• Sire: Malibu Moon
• Dam: Winner’s Ticket

Sea of Clouds’ People:

• Owner: The Sea Of Clouds Partnership
• Rider: Olivia Dutton
• Groom: Hannah Black

Sea Of Cloud’s Background

After selling as a yearling for $170,000 and racing twice with no placings, Sea Of Clouds retired from the racetrack and was sent to top eventer Phillip Dutton for retraining by his racing trainer Graham Motion. Motion and his wife, Anita, have earned a reputation for their holistic, horses-first approach to training Thoroughbreds for racing. After forging a partnership with Phillip through a mutual connection at Cosequin® in 2012, the Motions started sending racehorses who showed a lack of promise on the track to the eventing trainer to produce as event horses.

Sea Of Clouds went on to be the most successful Motion Thoroughbred in Phillip’s program, competing at the CCI5* level and finishing as high as 10th place (Kentucky 2022). At the end of 2022, he passed the gelding’s reins over to his daughter Olivia Dutton, who needed an experienced horse as she prepared to move up to the Advanced level of eventing.

“New-But-Not-New” Partnership

The 23-year-old eventer already knew “Socs” well, as he’d been in the Dutton program since his 3-year-old year. “I kind of grew up with him,” she said. Nonetheless, taking a horse who’s gone at the top levels of the sport from another rider—even someone as talented as her dad—is inherently challenging. Most eventers prefer to produce horses from their younger years rather than acquiring “going” horses, but she needed a horse who could help her learn as she moved up to the levels.

“I definitely took what my dad was doing with him and wanted to learn more about how I could help him,” Dutton explained. “My dad knew Socs was a bit quirky and I would really have to learn how to ride him, but he was also a tough Thoroughbred who could help me out of things and really teach me.”

For her, the success she’s found in this “new-but-not-new” partnership came down to the relationship she has with Sea Of Clouds. “Just building that partnership has really helped me with him,” she said. “He was used to my dad riding him, and my dad’s a strong guy. So, in the beginning it was a little trial and error getting used to each other. But our partnership has gotten so strong and we’ve helped each other out a lot.”

Sea Of Cloud’s Daily Routine

Dutton is a big advocate for turnout and barring inclement weather she always ensures her horses get turned out at night. “I find for Socs, especially, he really loves his turnout,” she said. “Mentally, I think that’s really important for them.”

Once Socs is brought in for the day, he’ll go in his stall for breakfast and then spends about 30 or 40 minutes on the walker to loosen up his joints and muscles. Usually, he also spends time on a VitaFloor platform to provide whole body vibration for faster exercise recovery before Dutton rides.

In the thick of the competition season, Dutton leans heavily on the cross-training method of riding event horses. Her weekly training focuses heavily on fitness, and she utilizes the gallop track on their property or nearby hills to do gallop, slow canter and trot sets. She also incorporates this fitness work with her usual flat rides about two times a week.

“He doesn’t need too much jumping,” Dutton noted about Socs’ jump training. “At most, we might jump two times a week but usually just once.”

Socs also benefits from the magic hands of equine physiotherapist Emma Ford, who’s spent many years working on horses at the Duttons’ True Prospect Farm. “Emma usually works on him twice a month and has made a huge impact on how he goes,” Dutton said. “Every time she works on him, he feels like a million bucks.”

At competitions, she makes use of the ActivoMed massage blanket before riding Socs to keep his body feeling loose and relaxed.

Sea Of Clouds’ Nutrition

Dutton noted the support Cosequin® has provided for her horses’ joint health. “Especially this past year, we really thought about which Coseqin® products would benefit Socs,” she said. “He’s currently on Cosequin® ASU Balance for joint, immune and digestive support, as well as their Calxequin® daily hoof support supplement. He was already on Cosequin®, but focusing on these additional areas of support has been great for him.”

She describes Sea Of Clouds as a bit of a picky eater, especially during the peak of competition season, so she and her team have navigated some challenges in keeping weight on him. “We also work with Triple Crown,” she noted. “Socs loves their Complete grain and has looked better than ever this year.

Dutton said it’s normal for horses’ bodies to change over time depending on their jobs and noted that Socs’ body has changed quite a bit since his racing days. “Each year he’s been in our program, he’s gotten stronger and stronger,” she said. “I would say putting a topline on him has been the lengthiest process. As a racehorse, he was used to lengthening his stride. So we use a lot of slow canters to help him get really comfortable with collecting. He’s naturally a really fit horse, so we just want to make him stronger and keep up that fitness.”

And she’s achieved that goal with the nutritional support Socs receives from her individualized feeding and supplementation program—and she hopes more goals will be reached in the future.

Loving Socs

“I started out wanting to do the Kentucky four-star. That was a dream I’d had for a very long time. He went so well I started thinking about other events,” Dutton said. “Both my dad and I thought Boekelo [CCIO4*-NC-L in the Netherlands, Oct. 10-13, 2024] would be a great experience for us and good for me to go overseas and put myself out there. I definitely want to see how we go at Boekelo, but I’m always thinking ahead. And a big goal of mine would be to compete at the Kentucky five-star in April.”

At the end of the day, though, Dutton’s relationship with Socs matters the most. It’s what keeps her coming back to the barn day in and day out.

“I’m really big on loving on my horses and grooming them myself and just spending that one-on-one time with them,” she said. “And that also means feeding them the best nutrition and keeping them in a quality program. They try so hard for us. So it’s important that we’re doing everything we can to keep them happy and comfortable.”

Sea Of Clouds’ Major Accomplishments

Finished 13^th (2021) and 10^th (2010) at CCI5* level with Phillip Dutton • 13^th at the 2024 Cosequin® Lexington CCI4*-S • Eighth in the 2024 MARS Bromont CCI4*-L • Next competing at the 2024 Military Boekelo CCIO4*-L in the Netherlands