Fats, like oils, can be useful additives to the equine diet, mostly as a source of calories (energy), but may also have added benefits for the horse’s coat condition and potential immune benefits.

All fat sources have approximately 9 megacalories (mcal) of digestible energy, which is more than two times the calorie density of corn, oats or most commercial feeds. Therefore, one measuring cup of fat would have significantly more than a measuring cup of grain mix. So a smaller amount of fat (by volume or weight) packs more calories into a diet very efficiently.

This allows you to increase the energy content of a horse’s diet without having to increase their grain meals. When horses have very high energy requirements (show jumpers, eventers, barrel racers and racehorses for example), it may be difficult for them to eat enough hay and grain mix to meet their calorie needs. Furthermore, due to the higher risks of digestive disturbances such as colic that are associated with higher grain intakes, due to their starch and sugar content, replacing some grain calories with fat calories may be a healthier option for your horse. Plus, it should be noted that adding in a cup of oil is likely cheaper than adding in the same energy volume of grain.

An athletic horse also has higher protein, vitamin and mineral needs than can be found in fortified grain mixes, but these increased needs are not to scale with the increased energy needs, and simply feeding more grain mixes to such horses would potentially result in overfeeding some nutrients. It should be noted that athletes that require bursts of power – such as leaving a starting gate or going into a jump-off – do need a good amount of starch and sugar in their diets to produce muscle glycogen, but these needs are typically met with most grain mixes.

Many commercial feeds have fat added into them already. Higher fat feeds (8% or higher) typically have higher energy (calorie) content and lower starch and sugar, which might be beneficial for horses that are sensitive to starch and sugar in their diet. Some horses appear to be sensitive to sugars, and get a “sugar rush” from higher carbohydrate feeds, so are more manageable on higher fat diets. Although fat is high in energy, it is a “cool” energy, and is not associated with behavioural changes.

Fats can have other benefits, particularly in commercially mixed feeds, where it can enhance mixing properties, and, in some cases, palatability. However, it is often difficult to form a pellet with too much fat in it, and shelf life might become an issue for feeds that try to incorporate too much fat into them. Therefore, if additional fat is desired for a diet, top-dressing is an easy way to add it.

While many different types of oils are available – corn, flaxseed, soya, vegetable, olive – they all have similar calorie contents. Therefore, if you are simply looking to increase the energy content of your horse’s diet, you should just find the cheapest available. Nutritional differences between fats lie in their actual structure, which is made up of different lengths of chains of carbon and oxygen units. When the carbon units are “saturated” with oxygen, they are saturated fats, and when there are double bonds between carbon units and, therefore, fewer oxygen units attached to the chain, they are considered unsaturated, or polyunsaturated if there are multiple double bonds. The position of the first double bond also designates if a fat is an “omega-3” fat (compared to omega-6), and these types of fats have notable additional health benefits. The best source of omega-3 fats for horses is flaxseed (linseed) oil, though the longer chained omega-3 fats, DHA and EPA are found in
fish oil.

Consumption of omega-3 fats (particularly in human research) has shown benefits to the immune system as well as being anti-inflammatory. Feeding the omega-3 fats DHA and EPA has shown notable benefits for brain and heart health, and they improve recovery after exercise. In horses, there is less research, but flaxseed oil has shown anti-inflammatory benefits and improves some aspects of immune function. Fish oil supplementation in horses has resulted in reduced heart rate in response to exercise (potentially showing greater cardiovascular efficiency) and also showed a tendency to decrease an inflammatory compound in joints following exercise training. Most horses will tolerate fish oil and eat it happily.

Fats can easily increase the energy density of the horse’s diet and are very safe to feed. Most horses can tolerate up to two measuring cups of oils per day, or until a horse’s stools appear shiny – which suggests the fat isn’t being absorbed.