ATKINS DIET…..IS IT GOOD FOR HORSES?
BY Karen E. Davison, Ph.D.
Manager – Equine Tech. Services, Purina Mills, LLC
The Atkins Diet, which is commonly known as the low carb or no carb diet, has received a great deal of press in the last few years. As is often the case, diet fads and trends for humans quickly find their way into the horse industry and now there is a suggestion that horses would be healthier on a low carb or even no carb diet. Unless we are going to convince a horse to eat ham and eggs for breakfast, we will not be able to feed him a no carb diet, but what about a low carb diet? Would that be better for him than current feeding practices?
Let’s take a minute to clear up carbohydrate terminology just a bit. Carbohydrates include sugars, starches and fibers, all found in pasture and hay. This makes a “low carb” diet for horses unrealistic. Horses consume a high carbohydrate diet even when they don’t receive any grain or sweet feed. There are differences in types and amounts of sugar, starch and fibers in forages and grains and these components provide the majority of the calories utilized by the horse. It is important to understand how they are utilized and may impact the health and performance of horses.
Dietary carbohydrates are grouped into two broad categories. Non-structural carbohydrates (NSC), include starch and sugars and are digested by enzymes primarily in the small intestine. The end product of NSC digestion is glucose which will be stored in the liver and muscle tissue as glycogen. Glycogen is the fuel that a horse uses during quick bursts of high intensity effort. Structural carbohydrates are found in plant cell walls and include cellulose, hemicellulose and lignin. Structural carbs are dietary fiber. The lignin component is indigestible and just provides bulk in the duet, whereas cellulose and hemicellulose are digested through fermentation by microbes primarily in the horse’s hindgut yielding volatile fatty acids (VFA.s). NSC that passes through the small intestine undigested will also be fermented in the hindgut. VFA’s provide a great deal of the horse’s energy needs, however, only one VFA can be utilized to make glucose, the others are used to make fat. The presence of NSC in the hindgut will increase the production of the VFA that is converted to glucose, however, this process isn’t as rapid or as efficient as glucose produced from NSC digested in the small intestines. Body fat is a good source of energy for the horse at rest and at very low speeds, but isn’t used to any significant degree during higher intensity work.
Feeding horses large amounts of grain with high NSC can overwhelm the capacity of the small intestine and cause what starch overload to the hindgut. This can actually cause a change in pH and change the microbe population, resulting in an increased risk of colic or founder. Research has indicated that the safe upper level of starch that can be consumed by the horse in one meal ranges from 2.2 – 4.4 lbs. That is a wide range, but taking the more conservative figure, it translates to roughly 4 lbs of oats per meal, due to the relatively high starch content of oats. To get 2.2 lbs of starch from Purina Strategy the horse would to eat 8.5 lbs of Strategy in one meal. With new Purina Ultium Competition Formula, a horse would have to eat 12.2 lbs in one meal. Most horses don’t eat that much Strategy or Ultium in the entire day, much less one meal. Due to the relatively lower NSC content of these two feeds compared to oats or many mixed grain rations, it takes a much higher volume to approach a starch intake that would negatively impact the hindgut health of the horse.
Currently, “low starch” or “low carb” horse feeds are being promoted to horse owners with suggestions that they are healthier for the horse. It is certainly accepted safe feeding management to restrict the total grain provided in a single meal to avoid digestive upsets. In addition, there are some horses with metabolic issues, such as polvsaccharide
Storage myopathy, that require horses to be maintained on a very low NSC diet. However, as owners of performance horses, especially those that perform quick turns and hard stops, it is important to remember that horses depend on glucose to replenish the fuel required to do that work. We need to be sure not to swing the pendulum too far into the “low carb” realm. Everything in moderation is the key.
