Psyllium plant (Plantago ovata - desert plantain) in Las Vegas, Nevada. © Stan Shebs
Psyllium has a specific use in the treatment and prevention of sand colic.
When mixed with water, it swells to up to 10 times its original volume, turning into a jelly-like substance which is thought to ease the passage of sand through the digestive tract.
The latest Equine Science Update reports on research at Montana State University conducted to see if adding psyllium to a horse's diet had an effect on glucose and insulin metabolism.
Researchers had noticed previously that psyllium had a beneficial effect on insulin sensitivity when taken by people with insulin resistance. They wanted to investigate whether a similar effect occurred in horses.
They used 16 healthy horses - eight mares and eight geldings - which they divided into four groups of four, each containing two mares and two geldings.
All horses were fed a diet of mixed grass hay and a commercial whole grain feed twice a day. Psyllium pellets were added to the grain ration of three groups at 90g, 180g, or 270g daily.
The fourth group received the same diet, but without added psyllium.
On the 60th day the researchers withheld food from the horses overnight. In the morning they collected blood samples before the morning feed and then every 30 minutes for six hours, to monitor the blood glucose and insulin concentrations.
The researchers found that, on average, horses that had been receiving psyllium for 60 days had lower average peak glucose levels after feeding and lower average glucose levels. Psyllium-fed horses also had lower peak insulin levels and lower average insulin levels after feeding compared with horses that had not received psyllium.
Dr Shannon John J Moreaux, Assistant professor of Equine Science at Montana State University, and one of the research team commented: "Psyllium could be especially beneficial to obese, insulin-resistant horses, or horses that are predisposed to developing laminitis because of metabolic syndrome".
He added that it was commercially marketed and readily available to horse owners, and when fed daily, may help to maintain lower post-feeding blood glucose and insulin levels.
But he added it was a small study carried out using normal horses. "Before we can conclude that psyllium will benefit insulin resistant horses, further research is needed using affected horses."
However, if it proves to be effective in insulin resistant horses it could provide a useful addition to the strategies available for managing this condition.
Dr Moreaux's team is now conducting a follow-up study on grazed horses.
He points out that carbohydrate-induced laminitis, or grass founder, is very common in the Rocky Mountain region in the spring and autumn.
"Our goal is to see if the psyllium might decrease intake, increase water intake or alter metabolism by measuring, among other things, insulin and glucose."
The researchers are also evaluating a suitable group of insulin resistant/equine metabolic syndrome horses to put on trial.