Horses with equine metabolic syndrome have a higher than normal risk of developing laminitis, a painful and crippling inflammation of tissues within the hoof. One of the factors that can trigger laminitis is an overly high level of insulin in the horse’s blood, a condition that is hard to normalize even by reducing dietary carbohydrates.

Recent research conducted at Montana State University suggests that a feed supplement could reduce insulin level and therefore decrease a horse’s chances of developing laminitis. Scientists designed the study to evaluate the effect of adding psyllium to equine diets. This material is derived from the seed husks of Plantago ovata, also known as desert indianwheat.

Psyllium has been used as a remedy for  sand colic in horses where its jelly-like consistency is thought to pick up intestinal sand or at least ease its passage through the digestive tract. Though this treatment seems to be more effective in some horses than others, psyllium has a loyal following among some owners who regularly add it to the feed trough in an effort to prevent sand colic.  

In the new study, researchers followed a clue from human research showing that dietary psyllium was beneficial in increasing insulin sensitivity for people with  insulin resistance. They divided 16 healthy horses into four groups, with each group containing two mares and two geldings. All horses received grass hay and a commercial grain product. Horses in three groups were also given psyllium pellets in amounts from 90 to 270 grams daily. Horses in the fourth group did not receive psyllium and acted as a control. The treatments were used for two months after which blood samples were collected before feeding and at intervals after the horses were fed. The samples were analyzed for blood glucose and insulin concentrations.

Results showed that horses getting psyllium showed lower peak and average glucose levels and also lower peak and average insulin levels after meals than horses in the control group. The researchers cautioned, however, that more research is needed before psyllium can be hailed as the cure for insulin resistance and a sure-fire prevention for laminitis. Because the study was conducted with horses that did not show insulin resistance, similar studies should be set up using insulin-resistant equines to see if the result would be the same. Tests should also be run on horses that are grazing pastures, as these animals have diets that differ substantially from horses ingesting their fiber as hay.