Is A Low-NSC Diet Right For Your Horse? Maybe.
By Nicole Rambo, Ph.D., Tribute Equine Nutrition
While we have become increasingly aware of the special needs of horses with sensitivities to starch and sugar, there remains a large population of our performance horses that can benefit from moderate inclusion of NSC (non-structural carbohydrates: starch and sugar) in the diet.
Non-structural carbohydrates are found in varying amounts in all feed ingredients, with the exception of ingredients that are solely comprised of fat. The largest source of NSC in most horses’ diets is forage. Hay and pasture particularly can be very high in sugars depending on the variety and growing conditions.
Both starch and sugar are absorbed in the small intestine as glucose. Glucose absorption is countered by the release of insulin from the pancreas to maintain blood glucose within normal ranges. In horses with insulin resistance or insulin dysregulation, the body is unable to adequately clear blood glucose with normal levels of insulin, and as a result continues to secrete insulin. Hyperinsulinaemia, or high blood insulin, can cause negative health impacts and increase the horse’s risk of developing laminitis. Consequently, we aim to minimize insulin secretion in horses with metabolic disorders by limiting the amount of NSC in the diet.
Horse feeds are often judged on their appropriateness for a given horse based on the percentage of NSC. While the percent of NSC in a pound of feed is valuable information, it must be taken in context with feed intake. A single pound of a 50 percent NSC feed would contribute the same quantity of NSC as four pounds of a 12.5 percent NSC feed (0.5 lb). Percent is not a unit of intake.
Research conducted by Tribute Equine Nutrition in conjunction with Cooperative Research Farms has indicated that blood glucose and insulin spikes following a concentrate meal are minimized in the normal horse if NSC intake per meal is limited to 0.1 lb per 100 lb of body weight. This is equal to 1.0 lb of NSC per meal for a 1,000 lb horse. Horses with metabolic syndrome should be limited to 0.05 lb per 100 lb body weight, and 0.025 lb per 100 lb body weight per meal in extremely sensitive horses.
When feeding a horse that is sensitive to NSC, evaluate both the percent of NSC and feeding rate when comparing different feed options. Focusing on feeds that provide energy in the source of highly digestible fibre and fat allows for lower feeding rates, which minimizes NSC intake.
While not all horses require an extremely low NSC feed, there has been a fundamental shift away from feeding traditional sweet feed to horses, which can be as high as 50 percent NSC. High NSC diets can contribute to hyper-excitability and also increase the likelihood of gastrointestinal upset, both of which contribute to decreased performance. Ulcer-prone horses especially can benefit from a reduction in NSC, because sugars can be fermented into acid in the stomach.
Diets providing a balance of energy from highly digestible fibre, fat, and a moderate inclusion of NSC support performance of the non-metabolically challenged horse while minimizing issues related to extremely high NSC diets. Low NSC concentrates may not provide enough glucose for glycogen repletion. Glycogen repletion between exercise events is key to maximize performance and decrease the risk of injury due to early onset fatigue.
As fitness increases, a greater proportion of fat can be utilized for energy, sparing muscle glycogen, which has the added benefit of decreasing lactic acid production. It was long held that horses had limited capacity for digestion and absorption of fat because they do not have a gall bladder. More recent work has found that horses can digest up to 20 percent of the total diet as fat; however, fat fed at this level has the potential to escape digestion in the small intestine and negatively impact fibre digestibility in the hindgut.
Feeding a high fat (10-12 percent) performance feed at recommended levels will not increase total dietary fat to the level where fibre digestibility may be impaired; however, care should be taken when supplementing additional fat with a high-fat feed.
Feeding a low-NSC product without consideration of fortification of other essential nutrients will not support optimal health and performance, and may not provide sufficient energy for recovery between exercise events for performance horses without metabolic disorders.
For more information on this topic visit Tribute Equine Nutrition.