Research has shown that pasture-induced laminitis occurs at times of rapid grass growth. The accumulation of certain carbohydrates including fructans, starches, and sugars known as Non-Structural Carbohydrates (NSC) in pasture forage during the spring, early summer and autumn, particularly after rainfall precipitate this laminitis.
Types of Carbohydrates
Carbohydrates found in equine diets can be divided into two types: Structural and Non-structural. Structural carbohydrates are often referred to as fibre and are critical in the equine diet. Non-structural carbohydrates (NSC) are sugars and starches that are broken down by enzymes in the horse’s small intestine into simple sugars. These simple sugars are absorbed from the small intestine and circulate in the blood as glucose. The hormone insulin removes glucose from the blood and stores it in the liver and muscle as glycogen, or when an excess amount of NSC is consumed, it is converted to fat and stored throughout the body. Common examples of non-structural carbohydrates in horse diets include cereal grains (oats, corn, barley, etc) and molasses. Research has shown that metabolic disorders such as Obesity, Insulin Resistance, Laminitis, Cushings, Tying-Up as well as behavioural excitability are associated with excess NSC (sugar and starch) and not with structural (fibre) carbohydrates in the diet. Expert nutritionists and veterinarians researching in this field have determined “low carb” to be less than 10% NSC.
We must carefully manage pasture turnout and forage and grain intake in horses and ponies that are at risk for developing laminitis or are currently affected. We also understand that horses suffering from insulin resistance (IR) and/or Cushings as well as horses and ponies with the ‘‘easy keeper,’’ phenotype that are often overweight or obese, and may be persistently hyperinsulinemic should also be managed carefully with regard to their carbohydrate intake.
The following points summarize current advice regarding strategies for avoiding high NSC intakes by horses and ponies at risk for pasture laminitis:
- Animals predisposed to laminitis should be denied access to grass pastures, particularly during the spring.
- At other times of the year, limit the amount of turnout time each day (e.g., 1–3 hours) and turn animals out late at night (after 8:00pm) or early in the morning, removing them from pasture by midmorning at the latest (before 10:00am, because NSC levels are likely to be at their lowest late at night through early morning).
- Alternatively, limit the size of the available pasture by use of temporary fencing to create small paddocks or use a grazing muzzle.
- Do not turn horses out onto pasture that has been exposed to low temperatures in conjunction with bright sunlight, such as occurs in the autumn after a flush of growth or on bright cool winter days, because cold temperatures reduce grass growth, resulting in the accumulation of NSC.
Animals denied access to pasture for most or all of the day, require provision of alternative feedstuffs. Horses at maintenance require approximately 2.0% of their body weight as forage or forage plus supplement to meet daily nutrient requirements. Sweet feeds should not be fed and the feeding of other ‘‘treats,’’ such as carrots and apples, should be discouraged. Lucerne hay or other legumes, such as clover, on average, have lower NSC content when compared with grass hay but have considerably higher calorie/energy content.
HYGAIN® Feeds also offers two forage-based low starch feeds completed with vitamins and minerals: HYGAIN ZERO® and HYGAIN® ICE®. HYGAIN® ZERO® is a unique Low Carb – Low GI feed for all horses, with less than 1.5% starch, less than 5.5% non structural carbohydrates (NSC) and absolutely no grain or grain by-products. HYGAIN® ZERO® was developed to support the specialised dietary requirements of horses and ponies with conditions such as Obesity, Insulin Resistance, Laminitis, Cushings, Tying-Up or Grain Intolerance. The unique Low Carb – Low GI profile however is suitable for any equine requiring a low sugar and starch diet.