The source of energy (or calories) provided in a horse's diet has a direct impact on how well a horse competes in any discipline. Focused research in the past decade has vastly improved our understanding of energy utilization in horses. In fact, it has been a major driver in changing how we formulate our feeds and what ingredients we now include in our horse feeds.
Where Do Horses Get Energy in Their Diets?
Energy comes from multiple sources in a horse's diet. This can be in the form of fiber (structural carbohydrates), sugar/starch (non-structural carbohydrates), fats, and protein.
As a reminder, forage provides most of a horse's fiber. It will also provide the horse with some sugar/starch and protein. Generally, there is minimal fat in forage (2-3%). In addition to forage, a horse's diet is usually supplemented with a horse feed that adds additional energy. This, too, can be in the form of fiber, sugar/starch and protein. Of these:
- Fiber is mostly utilized in the hindgut of the horse by the gut microbes, which convert fiber to volatile fatty acids (VFA). Acetate is the primary VFA used as energy by the horse.
- Sugar/starches are absorbed and converted to glucose. Glucose is the primary blood sugar used to power any horse. Excess glucose is converted to glycogen and stored in the muscles and liver.
- Fat is now known to be able to be utilized by the horse extremely well as an energy source.
- Protein is not normally not used as an energy source, except when horses are in starvation mode.
How Horses Use Energy
Every horse operates at an aerobic level of activity every day. Any sort of movement will require energy. For example, just the simple act of walking to a water trough will require the horse to operate at an aerobic level. When it comes to competition horses, disciplines that usually operate at a consistent aerobic level can include:
- Trail riding at a walk or short bouts of trotting.
- Low impact dressage.
- Endurance riding at a walk or short bouts of trotting.
When it comes to aerobic exercise, horses require oxygen to utilize the energy stored in their body. This allows the horse to convert either carbohydrates (sugar/starch) and/or fats to be used as fuel. It is important to remember when it comes to all competition horses, all will have some level of aerobic activity. For example, even the warmup before a race will have the horse working at an aerobic level of exercise.
This changes for the horse when they compete under an anaerobic level of activity. Here, a horse uses energy to power short bursts of intense activity. Disciplines that expose horses to anaerobic levels of activity include disciplines like:
- Polo
- Racing
- Barrel racing
- Eventing
During an anaerobic phase of activity, horses are not able to use oxygen to metabolize fats. Rather they use energy in the form of glucose; first, blood glucose and when that is depleted, they rely on glycogen that is stored in the muscles and liver. Glycogen is broken down into glucose, which, in turn, is the fuel the horse needs.
However, it is not uncommon for horses to deplete their glycogen stores after intense or longer duration bouts of activity. Here, you may notice your horse losing steam during a competition or performance. This is usually indicative of a horse that is depleting most of their glycogen reserves.
