May 24, 2019
Spring Grasses and Laminitis
It’s hard to imagine, but Spring grasses will be growing soon, so now is a good time to reevaluate your horse’s risk for laminitis. Sometimes referred to as “founder,” laminitis is inflammation within the hoof wall that leads to varying degrees of pain and lameness. Signs of laminitis include reluctance to walk, short-stepping, and shifting weight. Exactly how laminitis develops is still unknown, but some cases develop after grazing on new or stressed grasses during the spring. This has been associated with high levels of sugars, especially a type called fructans, in the grass. Sugars are produced through photosynthesis during the day, and stored as fructans. The levels of sugars can vary greatly depending on the balance between photosynthesis and growth. In general, the highest fructans level is in the bottom two inches of growth, as in new or overgrazed grass. Anything that stresses the growth of the grass such as cold and drought will also increase the fructan levels. The cold nights of spring can cause high levels of sugars to accumulate.
All horses should be slowly introduced to grazing over a few weeks to allow the gastrointestinal tract to adapt to these higher sugar levels, thus decreasing the risk of GI problems or laminitis. Horses that have a history of laminitis, overweight horses, and horses with endocrine disorders are particularly sensitive to the sugar and fructan levels. These high-risk horses should start with 15-30 minutes of hand grazing or turnout and build slowly over a few weeks. Grazing should be stopped and your veterinarian contacted if any soreness or reluctance to move is noted during this time.
Horses with an endocrine disorder called Equine Metabolic Syndrome (EMS) have a decreased sensitivity to insulin, which makes them more susceptible to high amounts of carbohydrates in the feed. These horses are “easy keepers” and often have regional fat deposits in the crest of the neck and around the tail head. Horses with EMS have a higher risk of developing laminitis, and the condition is often not diagnosed until after a flare. Ponies, donkeys, Tennessee Walking horses, and Morgans appear to be predisposed to having EMS, but horses of any breed may be affected. Horses of any age may have EMS. Your veterinarian can do some simple blood tests along with dietary assessment to evaluate for EMS. Dietary changes, exercise, and grazing restriction can help prevent laminitis in many of these horses.
While EMS can affect young horses, Equine Cushing’s Disease is a disease of older horses (>13 years old). Cushing’s, also known as Pituitary Pars Intermedia Disorder (PPID), occurs when age-related changes in the pituitary gland lead to increased production of certain hormones including cortisol. Increased cortisol can cause generalized weight loss, muscle loss, increased drinking and urination, depression of the immune system, and increased risk of laminitis. An early sign of PPID is lack of shedding out in the spring or long hairs especially along the legs. Since laminitis is common in horses with PPID and these horses often also have EMS, they may require grazing restrictions. Your veterinarian can do lab tests to determine if your horse has PPID and come up with a feed plan. There is no cure, but there is a medication to help control some of the signs of this disease.
Horses with EMS, PPID, or other risk factors for laminitis vary in the amount of grazing they can handle without problems. Some may need to be stalled or kept in a dry-lot. A Nibble Net or similar device will help keep them occupied with hay longer and also prevents potentially damaging spikes in sugar and insulin levels. A grazing muzzle is useful for horses that can tolerate some grass. This device has a small hole in the bottom that slows the horse’s grass intake. Some horses can graze for short periods of time when the levels of sugars and fructans are lowest. As long as the temperature is >40 F, the plant will utilize the fructans overnight, so the lowest levels are in the early morning hours between 6 and10 AM. Short, overgrazed pastures and new growth will have higher levels than healthy grasses kept between 6-8 inches tall. Similar periods of stress and increased sugar content can occur in grasses during the fall, so similar grazing restrictions should be followed.
Managing a horse with or at-risk for laminitis can be challenging. Your veterinarian can help identify risk factors and determine the best plan for your horse.
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