By: Dr Rosie Alcorn BVSc PG Cert VPS Cert AVP MRCVS
One of the most common phrases in equine nutrition is that a horse needs a low-starch diet. But what exactly is starch, and is it really that bad?
Starch is a complex carbohydrate that the body breaks down to produce glucose, which provides a primary energy source for various functions in a horse’s body, such as movement, breathing, and brain activity.
In horses, starch is easily digested in the small intestine with the help of the enzyme amylase. It consists of chains of glucose molecules that can quickly be converted into glucose, making it a fast source of energy. Once absorbed into the bloodstream, glucose triggers the release of insulin from the pancreas, helping to move glucose into cells for immediate energy use. Because of this quick availability, starch is often referred to as a "quick-release" energy source.
While fibre is the best energy source for horses, it takes time to break down. Horses in intense training or competition may need a quicker source of energy to refuel before their next session. This is where a higher-starch diet can play a vital role.
Take a racehorse in hard training, for example. Even with free access to haylage, a large part of its day is spent on activities like training (up to two hours), veterinary care, physiotherapy, farriery, swimming, and grooming. If the horse tends to eat less when people are around, it may struggle to meet its energy needs. A higher-starch diet, given in smaller, more frequent feeds, can help replenish its energy stores more efficiently.
Keyflow's BlackType range offers three products tailored to horses' varying needs. BlackType Power (18% starch) is designed for horses in intense work, BlackType Prime (14% starch) suits those in reduced work, and BlackType Sensitive (8% starch) is ideal for sensitive horses.
Similarly, event horses, especially those competing in long-format events, may need more starch to maintain their energy levels, particularly after cross-country phases. In dressage, some horses might benefit from a boost to maintain optimal performance. Since every horse is different, their diet should be tailored to their individual needs.
Despite its benefits, starch can cause problems in certain situations. As a quick-release energy source, it can be problematic for horses with metabolic disorders, as it can lead to rapid fluctuations in insulin and blood glucose levels.
Horses with Equine Metabolic Syndrome (EMS) or Insulin Dysregulation: These horses have difficulty regulating insulin, so it’s important to avoid feeds that cause large spikes in blood glucose levels.
Horses with PSSM (Polysaccharide Storage Myopathy) or Muscle Storage Disorders: These horses benefit from a stable insulin and glucose balance, which is why a low-starch diet is usually recommended.
Keyflow's Golden Oldies is a Veteran Balancer Mash with 7% starch and 2% sugar, safe for horses with EMS or PSSM.
Glucose can cross the blood-brain barrier, which means that for excitable horses, high-starch feeds can be like giving a toddler a bag of sweets and expecting them to focus on learning.
Starch is meant to be digested in the small intestine. If a horse eats too much starch, the small intestine can become overloaded, and undigested starch will pass into the hindgut. In the hindgut, starch can disrupt the microbiome, leading to digestive problems such as colic or hindgut acidosis.
Starch is neither entirely a saint nor a sinner—it depends on the individual horse and its specific needs. For horses in heavy work, starch can be an important part of the diet when fed correctly. However, for horses with metabolic issues, muscle disorders, or behavioural concerns, a low-starch diet may be more suitable. As with all aspects of equine nutrition, understanding the horse’s specific needs is crucial to making informed dietary choices.
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