No escaping insulin dysregulation for older horses, studies reveal

Increased insulin responses have been found in healthy older horses in two recent studies exploring the link between insulin, diet and aging.

This suggests that older horses, whether or not they have been diagnosed with insulin dysregulation, need an appropriate diet and management plan to help minimise the risks associated with insulin dysregulation such as laminitis.

Insulin is a hormone produced by the pancreas. The release of insulin signals cells, especially in the muscle and liver, to take up glucose from the blood. A high level of insulin in the blood (hyperinsulinemia) may or may not be accompanied by insulin resistance (failure of cells to respond appropriately to insulin).

This is why the new term “insulin dysregulation” is now used. It refers collectively to excessive insulin responses to sugars, and/or fasting hyperinsulinaemia and/or insulin resistance.

Two studies conducted by the Waltham Equine Studies Group, which provides the science underpinning the Spillers feed brand, in collaboration with Michigan State University, aimed to find out more about the relationship between insulin dysregulation, dietary adaptation, and aging to help guide more appropriate feeding regimens for senior horses.

Researchers learned that even healthy older horses have increased insulin responses, compared to younger horses, in response to a starch rich or starch and sugar rich meal.

Both studies investigated tissue insulin resistance and the insulin response in healthy adults compared to healthy senior horses adapted to diets with varying levels and sources of hydrolysable and structural carbohydrate (starch, sugar, and fibre).

Results from both studies showed insulin responses tend to increase with age in healthy horses, regardless of the diet they had been fed before evaluation. The insulin response, for example, was highest in the senior horses fed a starch-rich meal even when they had been adapted to such a diet.

Spillers research and development manager Clare Barfoot said the studies confirm that the energy sources used in the diet of senior horses and their effect on insulin dynamics need to be carefully considered.

“Practically, this means restricting the overall amount of starch and sugar in the diet especially for those horses that already have additional risk factors such as obesity, native breeding or PPID.”

These studies are two of several exciting Spillers research collaborations aimed at helping to benefit the lives of senior horses in the UK and around the world.

Rapson J.L. , Schott II H.C. , Nielsen B.D. , McCutcheon L.J. , Harris P.A. &  Geor R.J.   Effects of age and diet on glucose and insulin dynamics in the horse. Equine Veterinary Journal https://doi.org/10.1111/evj.12812

Jacob, S. I., Geor, R. J., Weber, P. S. D., Harris, P. A. and McCue, M. E. (2018), Effect of age and dietary carbohydrate profiles on glucose and insulin dynamics in horses. Equine Vet J. 50: 249 – 254. https://doi.org/10.1111/evj.12745