Bob Judd, DVM, DABVP (Equine Medicine), DABVP (Canine and Feline Practice)
It seems abnormal to recommend feeding high levels of fat to any animal, but feeding fat is beneficial to many horses. Fat is commonly used as an energy source for horses as it supplies two and one quarter times more calories per gram than carbohydrates.
Your horse can get the same number of calories by eating fat as eating carbohydrates and are able to eat less volume. Eating large volumes of carbohydrates can lead to gastrointestinal disturbances like colic and laminitis, so feeding fat for calories is a safer option.
Dr. Clair Thunes, PhD, Equine Nutrition Consultant with the publication The Horse, states that the horse’s body can only use fat as a fuel when working aerobically, or in the presence of oxygen in the tissues. However, this preserves stored glucose (called glycogen) for use during anaerobic work, such as intense exercise when tissues are without oxygen.
Dietary fat also increases absorption of fat soluble vitamins such as A, D, E and K, and can increase workout time before your horse feels fatigued.
Good quality pasture might have a fat content of 2-5% and this percentage may be less in hay. Pasture does have high levels of omega-3 fatty acids compared to the omega-6 fatty acids as does hay. However, concentrate feeds have higher levels of omega-6 fatty acids rather than omega-3 fatty acids, which can increase inflammation.
Because omega-3 fatty acids are actually anti-inflammatory, some folks supplement their horse's diet with omega-3 fatty acids. To increase omega-3 fatty acids in the diet, many companies are adding ingredients such as flax seed to increase both omega-3 and -6 fatty acids.
You can also add flax seed or corn oil to your horse’s diet to increase omega-3 fatty acids, but the ration may not be balanced. For this reason, it is recommended to use a high fat ration that is correctly balanced for horses compared to feeding vegetable oil.