Age can complicate managing already tricky metabolic diseases in horses

Metabolic diseases, including both insulin dysregulation (ID) and pituitary pars intermedia dysfunction (PPID, previously known as equine Cushing’s disease) occur commonly in horses. Estimates indicate approximately 20% of horses 15 or older have PPID, while the prevalence of horses with ID or a combination of ID/PPID remains unknown.

The most important pathological—involving disease or damage—condition of both ID and PPID horses is laminitis, referred to in this setting as endocrinopathic laminitis or hyperinsulinemia-associated laminitis (HAL). As with other forms of laminitis, horses with HAL suffer extreme pain, lameness, and compromised quality of life.

Rather than delving into the clinical signs and diagnosis of ID and PPID, we’ll move beyond the basics in this article, focusing on best practices for managing aging horses with ID, PPID, or both. The key areas of management we’ll describe include diet and exercise tailored to aged horses, as well as medications. Special consideration also goes to managing older horses with osteoarthritis (OA) and understanding end-of-life care.   

Feeding Aging Metabolic Horses

Without a doubt, diet is the cornerstone of managing metabolic horses to decrease postprandial (after meals) hyperinsulinemia, even if the horse is not overweight.

“It is crucial to limit nonstructural carbohydrates, which are the sugar and starch components of the diet, in horses with ID to control postprandial hyperinsulinemia,” says Erica Macon, MS, PAS, PhD, of the Department of Animal Science at Texas A&M University’s College of Agriculture and Life Sciences, in College Station.

Scientists derived original recommendations of feeding commercialized concentrates and hay with less than 12% NSC from research in healthy horses, and they theorized this level would be safer for horses with metabolic disease. Since then, Macon and other nutritionists have recommended low-NSC hays, decreased pasture access, and ration balancers.

“However, it’s important to recognize that individual horses may have different insulin responses to the same diet,” says Tania Sundra, BSc (Hons), BVMS, MANZCVS (equine medicine), of Avon Ridge Equine Veterinary Services, in Brigadoon, WA, Australia. “Factors such as genetics and the gastrointestinal microbiome likely play a role in this interhorse variability, though this has not been fully elucidated. While some sources suggest a stricter threshold of 10% NSC, the 12% guideline is generally considered appropriate for most horses. Monitoring your horse’s insulin levels and adjusting the diet accordingly remains the best approach to managing horses with ID.”

Macon also points out that “nutritionists are trying to move away from percent-NSC basis. We now recommend that horses with hyperinsulinemia are limited to 0.1-0.15 grams NSC/kilogram body weight (BW) per meal.”

Forage should form the basis of the diet, and horses in good body condition should be offered 2% forage BW. However, if horses need to lose weight this might need to decrease to 1.75% BW or even 1.5% BW.

“But no lower than 1.5% BW, otherwise you jeopardize the integrity of the hindgut,” Macon says. The hindgut refers to the cecum and large colon (or large intestine).

Sundra adds, “Ideally the forage will be split into multiple small meals to mimic a more natural feeding pattern and help reduce the postprandial insulin response by preventing large spikes in insulin that can occur with larger meals.”

Although some producers do have their hay analyzed, the technique might not be ideal or accurate, says Macon. But having a laboratory with an expansive database analyze hay is a crucial step in managing insulin-dysregulated horses, and both she and Sundra recommend it.

“Owners only need to test one batch at a time (i.e., same cutting or load of hay), not each bale,” says Macon.

Lean senior metabolic horses are much more difficult to manage than overweight animals because they need calories to maintain or put on weight, but they still need lower NSC concentrations.

“Most senior horses will experience sarcopenia (progressive loss of skeletal muscle mass), especially those with PPID,” Macon says. “We therefore need to feed quality, bioavailable amino acids. Ration balancers work very well for this.”

Sundra agrees, saying a senior metabolic horse’s diet needs to address both muscle maintenance and safe calorie intake. Her tips include:

• Manufacturers often formulate senior-horse-specific feeds to provide higher-quality protein (including the amino acid lysine) to help combat age-related muscle loss/sarcopenia;
• Calories (energy) should come from safe, low-NSC sources, such as beet pulp without molasses, fats, and oils (e.g., rice bran or flaxseed oil) rather than high-starch grains; and
• Forage should still be the foundation of the diet, with an emphasis on low-NSC hay or a soaked hay to reduce NSC content (be sure to discard the soaking water so the horse doesn’t consume it).

Including Exercise in Treatment

For horses with metabolic issues, especially those that are overweight, exercise should be a fundamental feature of management alongside nutrition. In fact, a combination of diet and exercise resulted in a greater improvement in insulin sensitivity in obese ponies compared to diet restriction alone (Bamford et al., 2019).

According to a survey by Herbst et al. (2024) of 2,700 owners of aged horses, 79% engaged in little structured exercise.

“I was involved in this project and, even though we know exercise is beneficial, the reality is that getting owners onboard is extremely challenging,” says Macon.

The following exercise recommendations come from the European College of Equine Internal Medicine (ECEIM) consensus statement on EMS written by Durham et al. (2019, tinyurl.com/yjnjn4dw):

In nonlaminitic ID horses, minimum recommendations include low-to-moderate-intensity exercise to achieve heart rates of 130 to 170 bpm for more than 30 minutes, more than five times a week;

In previously laminitic horses with recovered and stable hoof lamellae, minimum exercise recommendations involve low-intensity exercise on a soft surface to achieve heart rates of 110 to 150 bpm for more than 30 minutes, more than three times per week, while riders/trainers carefully monitor for signs of lameness.

However, in addition to owner commitment and the laminitic discomfort that limits a horse’s ability to exercise, OA might also contribute.

Arthritic Metabolic Horse Exercise

Among owners caring for aging horses, even without metabolic conditions, OA is a leading concern. In a recent survey of 2,717 U.S. horse owners, researchers found that 30% of horses had veterinarian-diagnosed OA (Herbst et al., 2024). Common methods of managing OA include administering non-steroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone or “Bute” or intermittently giving intra-articular (IA) steroids such as betamethasone.

Medication Effects on EMS Horses

François-René Bertin, DVM, PhD, an associate professor in large animal internal medicine from the Department of Veterinary Clinical Sciences at Purdue University College of Veterinary Medicine, in West Lafayette, Indiana, recently demonstrated that phenylbutazone does not increase insulin secretion in ID horses (Kemp et al., 2024).

Hypothesizing that NSAIDs might increase insulin secretion through prosteglandin E2 (PGE2, principal mediator of inflammation in diseases such as osteoarthritis) inhibition in horses, Bertin et al. administered either phenylbutazone intravenously for nine consecutive days or a saline placebo to nine healthy horses and seven horses diagnosed with ID. Horses then underwent testing to measure circulating insulin and glucose levels and, unlike in humans, insulin concentration decreased.

This suggests that in horses with ID, Bute decreases ID-associated inflammation and improves tissue insulin sensitivity, (crucial for glucose uptake and metabolism) leading to decreased insulin secretion.

“Those effects are rather mild but give us some insight about the role of inflammation in the development of ID,” says Bertin. “These data should not, however, suggest that phenylbutazone is a safe long-term treatment for (horses with) HAL. Instead, phenylbutazone can provide short-term pain relief without increasing insulin in metabolic horses with HAL.” 

Studies of IA corticosteroids do not bring equally good news. Instead, researchers widely report potentially harmful effects of corticosteroids even after a single joint injection. For example, in multiple studies, authors report significant increases in circulating insulin and glucose concentration following a single IA dose of triamcinolone, a commonly administered steroid for managing OA in horses.

Page and colleagues conducted a pilot study to determine the metabolic effects of the corticosteroid betamethasone in five healthy and three ID horses (Page et al., 2025). They injected 9 milligrams of betamethasone into each horse’s front fetlock joint before performing an oral sugar test and measuring adrenocorticotropin—ACTH, a hormone the pituitary gland releases—and cortisol levels (excessive ACTH amplifies cortisol secretion from the adrenals).

They found IA betamethasone had systemic effects on the horses, suppressing both ACTH and cortisol. 

“While it is unknown whether the temporary suppression of ACTH and cortisol is of significant detriment to horses, cortisol is an important hormone in stressful situations, so that raises the potential that these horses may not be able to respond properly to those situations,” Page explains. “There is also the concern that these drugs may cause a temporary immunosuppression, although work to better understand this is ongoing.

“While we were not able to make very many specific conclusions in this preliminary study, we did note that the metabolic effects of betamethasone were similar, albeit shorter lasting and smaller, than triamcinolone,” he adds. “As a result, we again recommended continued caution using corticosteroids in ID and/or laminitis-prone horses.”

Page says the group plans to expand on their work into other IA medications and larger groups of ID horses, given the importance of targeted treatment options for this horse demographic. In the meantime, for those looking for a noncorticosteroid alternative, Page and colleagues demonstrated that autologous protein solution (APS) administered IA did not exert any metabolic effects compared to triamcinolone in healthy horses, suggesting it could be a potential treatment option in ID horses (TheHorse.com/1132877).

Medications to Consider

Pergolide Veterinarians recommend treating PPID horses with pergolide. The 2023 Equine Endocrinology Group reports that clinicians should start with an initial pergolide dose of 2 micrograms/kg (0.5 mg for a 250 kg pony and 1.0 mg for a 500 kg horse) once daily (tinyurl.com/2a9a2wh7).

Practitioners might also consider prescribing cabergoline, a human drug Cabergoline used to treat different types of medical problems that occur when the body produces too much of the hormone prolactin.

Sodium-Glucose Cotransporter-2 Inhibitors (SGLT-2is) When indicated, SGLT-2is might benefit horses with ID. These medications increase urinary excretion of glucose, which in turn decreases the amount of glucose in the circulation. As a result, horses need less insulin to control blood sugar levels. Some published studies support the off-label use of various SLGT-2is, including canagliflozin, ertugliflozin, and velagliflozin, in horses.

“While SGLT-2is can be a valuable tool in managing severe hyperinsulinemia, these medications are typically reserved for cases that have failed to respond to dietary interventions or for severely affected horses where immediate insulin reduction is necessary,” says Sundra. 

She went on to describe four scenarios where she recommends an SGLT2i:

1. Short-term during transition to a low-nonstructural-carbohydrate diet;
2. Emergency use following accidental overconsumption of NSC-rich feed;
3. Preventively prior to corticosteroid administration; and
4. When managing chronic, severe, resistant equine cases.

“Some horses remain persistently hyperinsulinemic despite strict dietary control,” Sundra says. “In these refractory cases, an SGLT2i may be considered for longer-term management to maintain lower insulin levels and reduce the risk of laminitis. However, this should be closely monitored by a veterinarian, as long-term effects and optimal dosing strategies are still under investigation.”

Veterinarians prescribe these medications off label, relying primarily on clinical experiences for evidence of their effectiveness.

“In Australia and the U.K., ertugliflozin is most commonly used in clinical practice,” says Sundra. “The case studies we have published used a dose of 0.05 mg/kg once daily, but some animals might be controlled on lower doses.

“SGLT-2is should be carefully considered within the context of individual risk factors, and their administration should always be part of a comprehensive management plan that prioritizes nutrition, exercise, and overall metabolic health,” she adds.

Combining Pergolide, SGLT-2is Recall that many horses with insulin dysregulation also have PPID and could therefore need treatment for both conditions.

“There are no known interactions between the SGLT-2i ertugliflozin and dopamine agonists like pergolide or extended-release cabergoline,” Sundra explains. “However, it’s worthwhile mentioning that dopamine agonists can sometimes cause a temporary decrease in appetite, so if a horse is already on ertugliflozin and pergolide or extended-release cabergoline is being introduced, I always advise stopping the ertugliflozin for a few days to ensure the horse continues eating to reduce the risk of hyperlipemia (elevated lipid concentrations in the bloodstream).”

Critically Assessing Quality of Life

As one can imagine, it’s not easy managing chronic laminitis in addition to other age-related co-morbidities such as OA. Researchers have reported the prognosis for PPID is poor, with only 50% of horses surviving more than 4.5 years after being diagnosed (Johnston et al., 2025).

As difficult as end-of-life care can be to discuss, preplanning avoids last-minute emergencies and allows your older horses to live their final days with dignity. To successfully navigate the end-of-life phase, owners need to be able to critically assess their horses’ quality of life. In other species various quality-of-life tools are available. In dogs, for example, “The HHHHHMM Scale” (tinyurl.com/3drssxd2) takes the animals’ pain, happiness, mobility, and day-to-day engagement into consideration.

No comparable scale yet exists for horses, but in 2022 Long et al. collected data from 14 published studies on equine welfare that might help owners make informed decisions toward the end of their horses’ lives. They recommend that quality-of-life assessment includes both behavioral parameters to assess the horse’s mental state in addition to the physical state. They further suggest evaluating behavioral and physical parameters over time, stating that assessing quality of life remains an ongoing process, not a single event. 

Ideally, owners partner with their veterinarians to make this delicate decision together, ensuring horses’ best interest is always paramount, regardless of the emotional attachments.

Take-Home Message

Sundra says the greatest challenge in managing aging horses is ensuring a good quality of life while addressing the complexities of aging-related conditions.

“Chronic diseases occurring in older horses, such as OA, PPID, and ID, require proactive management to prevent pain, mobility issues, and laminitis,” she says. 

Nutrition and preventive care play a critical role in managing these diseases in our older horse populations. Early detection and intervention for conditions such as PPID and ID can significantly improve long-term treatment outcomes. “A precision-medicine approach, tailoring care to each horse’s needs, is key, as a one-size-fits-all strategy is unlikely to be effective,” says Sundra. 

This article is from the Older Horse 2025 issue of The Horse: Your Guide to Equine Health Care. We at The Horse work to provide you with the latest and most reliable news and information on equine health, care, management, and welfare through our magazine and TheHorse.com. Your subscription helps The Horse continue to offer this vital resource to horse owners of all breeds, disciplines, and experience levels. To access current issues included in your subscription, please sign in to the Apple or Google apps OR click here for the desktop version.