One could argue that the basics of equine nutrition haven’t undergone dramatic changes since the domestication of horses. “Back then,” when horses were primarily used for work, they were offered forage supplemented with grains, such as corn, oats, and barley. This is fairly similar to what most horses are fed today. But what we know now is there’s a lot more to feeding horses other than simply providing forage and concentrates in sufficient quantities for adequate energy.
For example, back in the 1950s and ’60s, when horses transitioned from being work animals to leisure/performance animals, nutritionists began recognizing they could modify the diet to improve performance. In 1975, Slade et al. reported that horses fed a diet containing 12% fat (9% added corn oil) then ridden 67 kilometers (over 8 to 10 hours) performed better and had higher blood glucose concentrations at the end of the ride than horses fed the control diet containing only 3% fat. Today, research groups (e.g., Burron et al. 2024) are focusing on omega-3 and omega-6 fatty acid supplementation to optimize the ratio of these fats and influence inflammatory responses, disease management, and overall health.
Since the mid-1900s, the field of equine nutrition has exploded with the same force as our horses’ waistlines. In the past year or two alone, research pertaining to equine nutrition has been prolific, involving studies on supplements, the intestinal microbiome, hay analysis, equine gastric ulcer syndrome, and obesity accompanying equine metabolic syndrome/insulin dysregulation. In this article, we’ll review some of the research and share the most practical and intriguing findings and updates.
Supplement Science
Several research groups have looked at the effect of supplementing equine diets with various fats. In 2024, Richards et al. found that camelina, flaxseed, or canola oil supplementation improved horses’ coat quality. Camelina oil comes from a low-input, high-yield crop and provides a greater amount of α-linolenic acid, an omega-3 fatty acid, than linoleic acid, an omega-6 fatty acid, compared to other dietary fat sources currently used in equine diets.
In a 2023 study, Li et al. examined a natural plant supplement called ellagic acid (EA) in year-old Thoroughbred horses. They theorized that EA could support the underdeveloped gastrointestinal tracts of young horses to promote feed utilization and growth. EA has antioxidant and anti-inflammatory effects (among others) and gets broken down by microbes in the intestinal microbiome to produce urolithins A and B, as well as isourolithin A, which might be responsible for its biologic effects. After supplementing the horses’ diets with either EA for 40 days, Li et al. found improved nutrient digestibility, a more diverse fecal microbiome, and enhanced growth. They concluded, “EA mediates these beneficial effects by regulating the abundance and diversity of intestinal flora, optimizing floral structure, promoting beneficial bacterial colonization, and stimulating the secretion of VFAs (volatile fatty acids) to inhibit pathogenic bacterial growth in the intestine, thus improving intestinal health and microfloral diversity.”
Recommending and Interpreting Hay Analysis
In recent years, commercial laboratories have made hay analysis services more available and affordable through a variety of analysis packages.
“Nutritional management of health conditions such as insulin dysregulation have highlighted the importance of having a hay analysis to know the nonstructural carbohydrate content of hays and determine suitability,” explains Catherine Whitehouse, PhD candidate at the University of Kentucky under the advisement of Laurie Lawrence, PhD. “But hay analysis is also an important management practice for determining the nutritional value of the hay, digestibility, and protein and mineral content. It can be a useful piece of information when developing rations for different classes of horses and selecting suitable hays.”
As part of her PhD work, Whitehouse and Lawrence distributed a survey to Kentucky Association of Equine Practitioners members to get equine veterinarians’ perspectives on selecting and evaluating hay for horses and the relationship between hay feeding practices, horse health, and behavior.
Results of that survey showed that while most veterinarians (78%) were very confident or confident about identifying hay types and evaluating hay quality based on sensory characteristics such as color and smell (73.2%), only 41.5% were very confident or confident in evaluating hay quality based on forage analysis.
“In fact, hay sampling and analysis services were not routinely offered to clients,” says Whitehouse. “Only 50% of veterinarians had submitted a sample for analysis, with the most-selected reason being to evaluate nonstructural carbohydrates (35%).”
When asked where they would refer clients requesting this service, 11% of veterinarians were unsure, while 67% selected county extension agent and 19% commercial lab.
Whitehouse says veterinarians who responded to the survey were familiar with the University of Kentucky Extension program and indicated they would recommend it to their clients looking for nutritional services such as hay sampling and analysis.
“This preliminary survey provides valuable information regarding nutrition-based interactions between veterinarians and their clients that can be used to develop educational materials,” Whitehouse says, adding, “The majority of veterinarians agreed it would be useful to have educational resources to share with their clients on selecting hay for different horse types, sensory evaluation of hay, and interpreting a forage analysis. We are looking to develop guidelines to help advise veterinarians and their clients on which chemical analysis to select to provide the necessary nutrient data for their intended goals and how to interpret and apply the results of hay analysis into practical feeding recommendations.”
The Elephant in the Barn
“Hands down, one of the biggest topics in equine nutrition in the past several years is obesity,” says Pratt-Phillips.
As highlighted by one of her own studies (Pratt-Phillips et al. 2023), obesity abounds even among athletes. In that study, 35% of 377 elite competitive hunter ponies were considered obese, with body condition scores of 7 or higher.
“These findings show that elite competition ponies are dangerously overweight and that adiposity may influence performance in a judged event,” Pratt-Phillips and her colleagues wrote. “This is of grave concern to the horse industry and needs to be addressed.”
In addition to the concerns associated with simply being overweight, studies have confirmed the link between obesity, equine metabolic syndrome, insulin dysregulation, and hyperinsulinemia-associated laminitis (HAL). Much research has also been generated concerning appropriate feeding of horses for weight management and improving insulin dysregulation (e.g., Macon et al. 2024).
“While the management of insulin dysregulation with diet and exercise has dominated the research front, the effect of obesity casts a wider net,” says Pratt-Phillips. “Reproduction, muscle health, and performance are also affected by obesity.”
For example, Fresa et al. (2024) report that in addition to contributing to metabolic disorders, obesity is associated with cellular dysfunction and an increase in reactive oxygen species.
Catandi et al. (2024) reported mitochondrial dysfunction in oocytes and granulosa cells, which could potentially contribute to impaired fertility. In that study, granulosa cells, follicular fluid, and cumulus-oocyte complexes were collected from follicles ≥ 35 mm during estrus and after induction of maturation in obese and normal mares. They found that “Obesity promoted several mitochondrial metabolic disturbances in granulosa cells, reduced L-carnitine availability in the follicle, promoted lipid accumulation in cumulus cells and oocytes, and increased basal oocyte metabolism.”
Finally, Pratt-Phillips and colleague Ahmad Munjizun reviewed obesity’s impact on exercise performance (2023) and found that obesity requires animals to perform at a higher workload, puts them at risk for heat stress, might contribute to gait abnormalities, and might hasten development of osteoarthritis.
“Overweight horses have to work harder, might not be able to perform as well as their leaner counterparts, and will likely have shorter performance careers,” Pratt-Phillips adds.
Conversations About Equine Weight Management
Because of the serious welfare concerns associated with obesity and the sheer number of affected horses, great effort is needed to swing the needle in the opposite direction where obesity is the exception, not the norm. Tamzin Furtado, BA(Hons), AdvDip, PhD, is a social scientist studying the horse owner psychological aspect of equine weight management and has conducted a significant amount of research the past several years on the role of human behavior in weight management. She has published several studies, including one exploring the psychology of equine weight management and identifying areas where behavior change might be better supported (Furtado et al. 2022).
“In the past, the veterinary field has assumed most owners of overweight horses either don’t know or don’t care that their horse is overweight, but this is not often the case,” she explains. “It is much more frequent for people to know their horse is overweight, at least on some level, but not have the time or capacity to change.”
She adds, “When veterinarians assume an owner doesn’t care, then the obvious way to ‘help’ the owner is by giving them new information. They may say, for example, ‘Your horse is fat. If he stays this way his health is at risk, you need to change now.’ Unfortunately, humans aren’t great at processing long-term risk, so this approach can make people feel defensive. In response, the mechanism owners use to protect themselves is, ‘That person is mean/they don’t understand me/what I’m going through.’”
Those owners, Tamzin says, are generally not being difficult; slow commitment to change is normal, psychologically speaking, and as a species we’re adapted to try not to change unless we must.
“To top this off, none of us likes being told what to do,” Furtado says. “Therefore, trying to make it simple for people (e.g., by telling them how to change by doubling the exercise and soaking the hay) can make people more resistant to change as they rehearse in their head all the reasons they can’t follow the advice they’ve been given.”
Nevertheless, we need to help these owners but with an understanding of the process of change.
“Behavior change science tells us that people are much better at making changes if they’re in a positive frame of mind, they feel supported by others, and they feel the change is their choice. This is called self-autonomy theory,” relays Furtado.
So, instead of “telling” owners, Furtado recommends inviting people into the conversation and using their own ideas, which is shared decision-making.
For example, starting a conversation about weight by asking, “What do you think of the horse’s weight at the moment?” allows the practitioner to get information about the owner’s awareness of their horse’s obesity, what language they’re comfortable with, and how ready they are to talk about it.
“This same approach can be used throughout the conversation, asking questions like, ‘What do you think would be the best way to manage his weight?’ and ‘Would you like me to help tailor that with you?’ This approach is much more positively received than the standard, ‘Do this, this, and this,” Furtado says.
Feeding in the Future: Embracing Equine Nutritionists
Furtado also published a study on addressing weight management using the science of human behavior change (2021). “That article considered the veterinary-client interactions from a behavior change psychology perspective to determine how veterinary professionals can best assist owners,” she says. “An approach based on supportive and empathetic conversation is best for leading discussions on weight management, alongside tailored weight loss solutions which are agreed by the owner and the vet.”
Such discussions and tailored medicine, however, are not always possible for primary equine practitioners because of constraints such as time, patience, or knowledge about change behavior.
This is why Furtado, Pratt-Phillips, and other nutritionists agree that veterinarians should consider partnering with nutritionists to tailor diets with owners committed to their horses’ weight loss journeys.
“Practitioners can also work with other members of the horse’s health care team, such as farriers and physiotherapists, because all these people have an interest in helping maintain healthy body condition, but for different reasons,” adds Furtado.
In sum, Pratt-Phillips says, “Obesity increases the risk of laminitis, metabolic dysfunction, and arthritis and has negative consequences on reproduction and performance. These issues can decrease the quality of life for horses. Experienced and formally educated equine nutritionists are available to help horse owners and their veterinarians make dietary management plans to reduce and avoid obesity and improve the welfare of our horses.”
Sentinel’s equine nutrition team is available to help you and your practice make dietary recommendations, educate clients, and provide your patients with quality nutrition. Submit your nutrition questions and get expert advice at KentFeeds.com/vet-hub.
This article originally appeared in “Feeding for the Future: Nutrition Knowledge for the Modern Equine Practitioner,” brought to you by Sentinel Horse Feeds. You can download the complete issue here.
Related Reading
- Equine Gastric Ulcer Syndrome: Diet & Management Strategies
- Storage’s Effects on Commercial Equine Grains
- Effects of Adding Rice Bran to the Equine Diet
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