Laminitis in horses can strike any time of year, for a variety of reasons, but veterinarians and horse owners see endocrinopathic cases most commonly in spring and autumn. Understanding your horse’s risk level for this painful and potentially deadly hoof condition—and the physiological differences between spring and autumn laminitis—is critical to prevention.

Laminitis is a condition where inflammation in the laminar junction leads to the separation of the epidermal and dermal laminae in the hoof, which are basically what suspend the coffin bone within the hoof capsule. “For horses suffering from endocrinopathic laminitis, the trigger is an alteration to the metabolic state,” says Anna Garland, MS, a PhD candidate in equine physiology at the University of Guelph, in Ontario, Canada. “Over prolonged periods, if horses consume large concentrate meals or high-sugar forage, there will be an increase in the insulin response”.

The higher sugar levels in grass during the spring and autumn months are a key reason why laminitis is more prevalent during these times of year. “With the increase in insulin, an inflammatory response is triggered in the hoof; this increases the blood flow and delivers high volumes of insulin to the tissue,” says Garland.

How is Autumn Laminitis Different?

New growth of lush pasture triggers laminitis episodes in the spring, but different factors are at play in the fall. “There are two reasons why horses and ponies might experience endocrinopahtic laminitis in the autumn—nutrient changes in pasture and forage, and a metabolic shift,” says Erica Macon, MS, PhD, assistant professor of equine science at Texas A&M University, in College Station. These nutrient shifts often occur due to the start of colder nights and shorter days, she explains. And, “in the later autumn, hard frosts can make grasses retain their sugar content.”

Horses also experience a metabolic shift during autumn to prepare for winter, which can trigger a laminitis episode, she adds.

In her own research Macon found that horses with insulin dysregulation had the highest basal (resting) and post-oral sugar test insulin concentrations in the spring, but winter insulin concentrations in the metabolic horses were very similar to spring values. “Logically, it makes sense,” says Macon. “As we start approaching the colder months, horses start to pack on the fat to get them through the winter. … Insulin secretion goes up to promote the storing of fat. Thus, the body starts to shift to fat storage as the animal approaches winter, which increases insulin secretion, subsequently increasing the risk of laminitis.”

Autumn Equine Lifestyle Changes

During the summer months most horses are generally ridden more but, as winter approaches, show season winds down, and the months get colder, leading to a decrease in horses’ workloads. Reducing horses’ exercise in this way can negatively impact metabolic state. In a time when pasture sugar levels rise and horses begin to store fat for winter, “reducing exercise will only exacerbate fat storage,” says Macon. “I highly encourage exercise in the winter—even if you are just (working) your horse in the round pen for 15-20 minutes each day.”  

How Can I Detect and Prevent Autumn Laminitis?

Pillars of proper management of laminitic horses include recognizing their endocrine levels and managing housing, farrier care, exercise, and nutrition.

“First, horse owners need to know the endocrine status of their animal,” says Macon. “Have them tested for insulin dysregulation (or equine metabolic syndrome) and pituitary pars intermedia dysfunction (PPID, formerly known as equine Cushing’s disease).” If your horse is predisposed to endocrine disease (e.g., he’s overweight or obese), limiting nonstructural carbohydrates in his diet can help prevent the onset of laminitis, she adds.

When horses have comorbidities such as PPID, are obese, or are genetically predisposed to metabolic problems, their risk of developing autumn laminitis is higher, says Macon. “To be safe, my recommendation is to not allow horses and ponies that are at risk of endocrinopathic laminitis to graze on frosty autumn grasses/legumes,” she says.

Our sources recommend creating a unique management strategy for each horse because horses typically have individualized metabolic needs. If you know your horse is at risk for developing laminitis, and you are in a geographical region where autumn and winter have frosty nights, be sure to devise a plan to reduce your horse’s risk and avoid severe episodes. “Working closely with your farrier, veterinarian, and equine nutritionist is vital to creating a proper individualized management plan for your horse,” says Garland.

Decreasing your horse’s access to nutrient-rich forage (e.g., autumn frosty pasture), as well as incorporating regular exercise into their management plan can help reduce his risk of developing autumn laminitis. “Ideally, these at-risk horses will be housed on a dry lot with access to low-carbohydrate hay, but that is not always possible for most horse owners,” says Macon. “Therefore, giving horses shorter turnout times with a grazing muzzle is recommended.”

Ideally, turn horses out when pasture sugar content is at its lowest in the very early morning (generally 4AM until sunrise). Also keep in mind overall dietary balance. “In order to meet your horse’s nutritional requirements (i.e., protein, vitamins, and minerals)—which will not be met by your horse’s low-carbohydrate hay—you will need to feed a ration balancer,” notes Macon.

Take-Home Message

Understanding why autumn pasture poses a danger to at-risk horses and recognizing the seasonal metabolic shift that occurs can prompt horse owners to reduce their horses’ risk of developing endocrinopathic laminitis. Ultimately, the horses’ turnout schedules and balanced diets might need to fluctuate with the season. Evaluating your horse’s body condition in every season will help you determine what changes are necessary to maintain it optimally year-round.