Enhancing horse productivity and wellbeing has drawn considerable interest in feeding fat supplemented diets to horses. Much of this interest has been prompted by a significant amount of research on the subject over the last 10 years. 

Whilst several unknown aspects of specific fatty acid nutrition in the horse still exist, the caloric and some extra caloric effects of feeding fats to horses are well documented. 

These benefits include increasing energy content of the diet, enhanced body condition in thin horses, diminished excitability, increased oxidative capacity in performance horses and act as a carrier for fat-soluble vitamins.

The following article is a discussion of feeding fats to horses.

What is fat?

The type of fats (lipids) fed to horses are known as triglycerides, consisting of three fatty acid molecules attached to a glycerol molecule.

The chemistry of the fatty acid molecules determines if the fat is a saturated fat or unsaturated fat. Saturated fats contain no double bonds in the fatty acid chains and are solids at room temperature.

A common example of saturated fat is lard or tallow. Unsaturated fats (oil) contain double bonds and are liquids at room temperature.

Examples of oils fed to horses include corn oil, soybean oil and canola oil. The location of the double bond within the fatty acid is also used to identify omega 6 and omega 3 fatty acids.

The location of the double bond indicates the fatty acid will have a different fate within the body.

Research is ongoing to determine the proper amount and ratio of the different types of fatty acids that should be present in the diet.

Sources of fat

Practically speaking, the use of saturated animal fat is not common in commercial grain concentrates formulated for horses. Instead, the use of unsaturated oils (vegetable oil) is the preferred method of fat supplementation.

Common vegetable oils fed to horses include corn, soybean, canola and rice oil. These sources are each 100% fat.

Other fat supplements include spray-dried vegetable fat, which is 99% fat, high-fat stabilised rice bran, which is 20% fat, textured and pelleted feeds supplemented with fat that typically range from 6-12% fat, and a host of other supplements that have various amounts of fat.

Each of these sources of fat are palatable, given the horse has been slowly adapted to the fat source.

A relatively new source of fat is fish oil, which is high in omega 3 fatty acids. This oil is less palatable to horses, but horses can be adapted to it.

Is fat digestible?

Unsaturated vegetable oil (corn oil, soybean oil, canola oil) is highly digestible, in excess of 95% digestible by horses.

This oil is digested in the small intestine.

Horses can digest large amounts of oil, up to 20% of the total diet.

How many calories are in fat?

Vegetable oil contains approximately 2.5 times more digestible energy as an equal weight of oats and 2.3 times as much digestible energy as an equal weight of cracked corn.

Vegetable oil is easily the most caloric dense ingredient used in horse diets.

Is fat safe to feed? 

Fat should be gradually introduced into a horse’s diet over a 14 day period. If horses are not properly adapted to fat and too much is fed, the horse may refuse the feed or if the feed is consumed a transient diarrhoea may result.

Unlike grain, over-supplementation of dietary fat does not result in colic or laminitis. In humans, a high fat and cholesterol diet has been associated with coronary heart disease.

This condition has not been demonstrated in horses supplemented with fat. A horse on a ‘high-fat’ diet may receive 20% of their calories from fat; by comparison, our typical diet provides 40% of our calories from fat. If you frequent fastfood establishments you may be receiving up to 70% of your calories from fat.

So, a horse on a high-fat diet is really a misnomer, compared with a human diet.

How much fat can be fed? 

Horses are capable of digesting large amounts of fat. In carefully controlled scientific experiments, horses have been fed as much as 230g of oil/kg of diet or approximately 11 cups of oil per day.

Practically speaking, the maximum amount of oil top-dressed to feed would not exceed 2 cups/day for a 500kg horse. More oil can be fed in special circumstances, but all sources of fat should be gradually introduced into the diet to avoid feed refusal and diarrhoea.

Potential benefits of feeding fat

Safe calorie sources for weight gain

Vegetable oil, such as rice bran, contains approximately 2.5 times more digestible energy than an equal weight of oats and 2-3 times as much digestible energy as an equal weight of cracked corn.

Feeding rice bran oil supplemented feeds is a safe and effective method to put extra calories in the horse’s diet.

The increased calorie content can boost body condition in thin horses, diminish excitability, increase oxidative capacity in performance horses and act as a carrier for fat-soluble vitamins.

Adding fat to the diet may also decrease the amount of grain in the horse’s diet – providing a safer method of supplying calories, without adverse risks.

Reducing levels of starch intake may decrease the risk of feed-related disorders, such as colic, laminitis, acidosis, equine metabolic syndrome (EMS) and pituitary pars intermedia dysfunction (PPID or Cushings).

Effects of feeding fats on sporting and racing horses

Undoubtedly, the most dramatic effects of feeding fat supplemented diets to horses have occurred in the equine athlete. Horses that are adapted to dietary fat have an increased oxidative capacity, and spare muscle and liver glycogen during aerobic exercise.

Studies have shown fat is a major source of energy when exercise is below 75% of maximum aerobic capacity (VO2Max). This means a large group of performance horses, including endurance horses and many types of show horses, can utilise a large amount of dietary fat.

Additionally, supplementing fat to the diet of any equine athlete will result in metabolic advantages, such as reduced feed requirements for a comparable amount of work, reduced heat production, reduced thermal load and maintenance requirements for thermal regulation, and increased energy available for work.

Also, production of power and stamina can be increased for several seconds in the horse performing short-term, high-velocity exercise by an appropriate adaptation to a fat supplemented diet.

It has been shown race horses can run faster at a constant heartrate, and cutting horses can stop and turn harder for a longer duration after appropriate adaptation to correctly formulated fat supplemented diets.

Some of these effects are due to the caloric benefits described earlier, but the primary effect is due to the improvement in glycogen storage and mobilisation that results from feeding a fat supplement.

It appears the initial onset of acute fatigue in the performance horse is the depletion of glycogen stores in the liver and muscle.

Thus, feeding an appropriately balanced fat supplement, along with a correctly designed training protocol may offer great promise as a way to improve performances and perhaps reduce the frequency of injuries.

Effects of feeding fats on pregnant and lactating mares

Energy balance and body fat are major factors in reproductive performance in mares. The addition of dietary fat can help mares maintain energy balance and body fat reserves, especially when feed intake is limited during late pregnancy.

Research showed when lactating broodmares were fed fat supplemented diets, the concentration of fat in milk increased, and their foals grew faster, compared to their counterparts which were fed conventional, low-fat diets.

Feeding fats during sales and showing preparation

A sleek, shiny hair coat is necessary for both show and sale horses. A quality hair coat is partially dependent on providing horses with essential fatty acids for healthy skin and hair.

Tying up syndrome

High grain diets are a potential problem for horses with two forms of exertional rhabdomyolysis. Unfit horses with polysaccharide storage myopathy (PSSM) benefit from daily exercise, removal of grain and the addition of fat to provide the necessary calorie intake.

Fit horses with recurrent exertional rhabdomyolysis (RER) can maintain high calorie intake if the amount of grain in the diet is reduced and the amount of fat in the diet is significantly increased. In both of these forms of tying-up, dietary fat helps to minimise symptoms.

Recent research has shown many such horses improve markedly on a diet in which 20-25% of their energy needs are provided by fat.

Fats at a glance

  1. Fats (lipids) in the form of triglycerides are added to equine diets.
  2. Saturated fat is solid at room temperature. Examples of saturated fats include tallow and lard. These fats are not typically fed to horses.
  3. Unsaturated fat (vegetable oil) is liquid at room temperature. Examples of unsaturated fats are corn, soybean and canola oil.
  4. Unsaturated vegetable oil is highly digestible, greater than 95% digestible in horses.
  5. Fat is extremely energy-dense, containing approximately 2.5 times the digestible energy as an equal weight of corn or oats.
  6. Large amounts of fat can be fed, provided the horse is properly adapted to fat. Normally, a maximum of 2 cups/day can be top-dressed to feed for a 1000lb horse.
  7. Fat is recognised as a safe energy source for weight gain.
  8. Fats can help alleviate symptoms of tying-up in certain horses.
  9. Fats have positive influence on exercise performance. These horses will spare muscle glycogen and have an increased oxidative capacity.
  10. Fats are useful in broodmare diets to assist in maintenance of energy balance and body fat reserves.
  11. Fats provide essential fatty acids necessary for healthy hair and skin. Show and sales horses benefit from the addition of fats to the diet.