By: Dr Rosie Alcorn BVSc PG Cert VPS Cert AVP MRCVS
One of the most common phrases in equine nutrition is that horses should be fed a low-starch diet. But what exactly is starch, and is it truly harmful for every horse?
Starch is a complex carbohydrate that the horse’s body breaks down into glucose. Glucose is the primary energy source for essential functions such as movement, breathing, and brain activity.
In horses, starch is digested in the small intestine with the help of the enzyme amylase. It is made of chains of glucose molecules that can be rapidly converted into energy. Once glucose enters the bloodstream, it triggers the release of insulin from the pancreas. Insulin helps glucose move into cells where it can be used immediately. Because starch is quickly available, it is often referred to as a quick-release energy source.
Fiber is the best long-term energy source for horses, but it breaks down slowly. Horses in heavy work or high-level competition may require a faster source of energy, and starch can play an important role in meeting those demands.
Take a racehorse in full training, for example. Even with free-choice hay or haylage, much of its day is spent exercising, receiving veterinary care, undergoing therapy, working with the farrier, swimming, and being groomed. If the horse eats less due to a busy environment, meeting energy requirements can be a challenge. Small, frequent meals that include starch can help replenish energy efficiently.
Upper-level event horses may also benefit from starch to maintain energy, particularly following demanding cross-country phases. Some dressage horses benefit from extra starch to sustain performance during long training sessions. Every horse is an individual, and starch can be used strategically to match specific energy needs.
Despite its benefits, starch can cause issues in certain situations. As a rapidly available energy source, it may be unsuitable for horses with metabolic or muscle disorders, and it may contribute to behavioral and digestive problems.
Horses with metabolic conditions such as Equine Metabolic Syndrome (EMS) or Insulin Dysregulation struggle to manage blood sugar levels. Large glucose spikes from starch can be harmful.
Horses with Polysaccharide Storage Myopathy (PSSM) and other muscle disorders benefit from steady glucose levels, making lower-starch diets a better option.
Excitable horses may react to quick energy from starch, leading to behavioral issues. In addition, excessive starch intake can overwhelm the small intestine. When undigested starch reaches the hindgut, it can disrupt microbial balance and increase the risk of digestive upset, including colic and hindgut acidosis.
Starch is neither entirely good nor entirely bad. For horses in intense work, it can be a valuable dietary component when fed correctly and in appropriate amounts. For horses with metabolic challenges, muscle conditions, or sensitivity to quick energy, a lower-starch approach is often safer. The key is understanding each horse’s individual needs and tailoring the diet accordingly.
United Kingdom
International Stockists
