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

Dietary fats are also known as triglycerides--there are three (tri) fatty acid molecules attached to one glycerol molecule. These fatty acids can be saturated or unsaturated. There can be considerable variation in the size or length of the fatty acids. Fats with unsaturated and/or short fatty acids tend to be in the liquid state at room temperature and are referred to as oils. Conversely, longer chain fatty acids that are saturated usually are solid at room temperature and are referred to as fats.

For the equine we are mainly concerned with the short chain fatty acids known as oils. Within this article, the word "fat" will refer to both fats and oils.

Palatability or Acceptability of Fat Supplemented Diets

Most horses readily accept fat supplemented grain mixes containing up to 10% added fat. Occasionally a timid or "finicky" eating horse may require more time before readily consuming a fat supplemented diet. Most horses will resume their normal feeding behaviour after consuming three to five meals containing a fat supplement. Of course, this assumes the fat is of high quality and is not rancid. When feeds contain very large amounts of fat (greater than 10% by weight), it takes longer for horses to readily accept the diet. For best acceptability, fat should be introduced into horses' diets in small amounts (50 –100g per meal), then gradually increased over at least a week, until the desired concentration of fat in the diet has been reached.
Generally, horses accept high quality vegetable oils more quickly than lower quality oils or animal fats. In recent times with animals being fed animal by-products and the outbreak of Mad Cow Disease I feel that feeding mammalian by products will be banned. For best results, fat should be incorporated directly into horse feeds, but fat supplements can be mixed into the feed in the feed bin. Topdressing a fat supplement is easier with textured feeds than pelleted feeds.

Digestibility of Fat Supplemented Diets

Fats are extremely high in energy (34-39MJ/Kg), which basically means that fats are around 2 ½ times more energy dense than average oats or barley.

The digestibility of fats in the equine diet is normally quite high due to the fact that fats are almost entirely digested in the horses small intestine, and the small amount of fat that escapes digestion in the small intestine does not seem to have harmful effects on fermentative digestion in the caecum and colon.

The digestibility of energy in vegetable oils can be 90% or more, while animal fat is usually near 75%. However, over 95% of the digestible fat in fat or oil is digested in the small intestine. Thus, diets for horses can contain greater amounts of fat than those for ruminants without creating negative effects on the digestion of other diet components. Therefore, feeding fat is a very effective and safe way to increase the energy intake of horses with high-energy requirements.

Since fat is digested enzymatically in the small intestine and can be substituted into horse feeds in place of starchy ingredients, fermentative digestion of starch can be reduced in horses with high feed requirements. This will reduce the likelihood of colic, acidosis or laminitis frequently associated with feeding large amounts of starchy feeds.

With fats being extremely digestible in the horse, the horse is getting more value weight for weight than carbohydrate rich grains without the problems such as colic, laminitis and acidosis from grain overload.

Metabolic Effects of Feeding Fat Supplemented Diets

Several metabolic advantages exist when feeding fat supplemented diets to horses. Several studies have shown that the digestible energy in fat supplemented diets is used more efficiently by the horse than that in conventional low fat diets. For example, adding fat to the diet reduces the amount of heat energy lost and increases the net energy available for reproduction, lactation, growth or work. This is due primarily to a reduction in feed requirements and a reduction in the heat caused by fermentation, both of which contribute to lower heat production. Also, lower heat production reduces the thermal load on the horse, and thus, reduces their maintenance requirement during hot weather. This aspect is extremely important to horses competing in sub and tropical environments where temperatures are constantly above 25°C.

Perhaps the most dramatic and useful result of feeding fat supplemented diets to horses is the extra caloric effect on energy metabolism in the equine athlete. When fat is substituted into the diet of horses that perform short term, high-velocity exercise, and the horses are allowed sufficient time to become adapted to the diet, it has a sparing effect on muscle glycogen in the muscle of adapted horses, which can be mobilized to produce energy anaerobically during short bursts of maximal power output.

The storage and retrieval of glycogen is essential for elite equine athletes, who require a short-term supply of energy when they reach a state of oxygen deficiency during performances/races. It is important to note that this sparing effect on glycogen stores in horses adapted to a fat supplemented diet occurs only when the horses are fed a diet containing sufficient carbohydrates to facilitate the enhanced storage of glycogen. Further, the horses must be trained appropriately for the glycogen sparing effects of feeding fat to be realized. The adaptation period for glycogen sparing to occur is generally between 3-4 weeks and the amount of fat in the total diet needs to be around 10% of their caloric requirements.

Effects of Growth

The effects of feeding fat supplemented diets to growing horses appear to be primarily caloric- most, if not all, of the response is a reflection of the number of calories fed. Weanlings and yearlings fed fat supplemented diets will gain weight faster and may be more efficient, due to lower feed requirements, than when fed conventional diets, but responses can easily be explained by differences in calorie balance.
It is particularly important to rebalance growing horses' diets when fat is added to maintain necessary nutrient: calorie ratios. When growing horses have been supplemented diets that were balanced to correct nutrient: calorie ratios, no detrimental effects on skeletal or other developments have been reported from controlled feeding trials.

Effects on Reproduction and Lactation

The benefits of feeding fat to broodmares have also been related primarily to caloric and metabolic effects discussed previously. However, recent work indicates that feeding fat to broodmares may alter the lipoprotein profile in the blood, thus affecting the synthesis of the endocrine compounds involved in regulation of reproduction.

There is some indication that feeding fat supplemented diets to broodmares, even at a comparable energy intake, may shorten the postpartum interval and increase conception rates. (This may in fact be related to oil tochepherol (Vitamin E) levels.
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.

Effects on Performance/Race Horses

Undoubtedly, the most dramatic effects of feeding fat supplemented diets to horses has occurred in the equine athlete. Further, these effects are more pronounced in horses that must work anaerobically during a significant part of their performance. Adding fat to the diet of any equine athlete will result in the metabolic advantages previously described- reduced feed requirements for a comparable amount of work, reduced heat production, reduced thermal load and maintenance requirements for thermal regulation, increased energy available for work, etc. In addition to these caloric effects, it is now known that production of power and stamina can be increased for several seconds in the horse performing short-term, high-velocity exercise by appropriate adaptation to a fat supplemented diet.

It has been shown that race horses can run faster at a constant heart rate 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 mobilization that results from feeding a fat supplemented, high carbohydrate diet for a sufficient period of adaptation. It appears that 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 supplemented diet along with a correctly designed training protocol offers great promise as a way to improve performances and perhaps reduce the frequency of injuries to elite, equine athletes.

Tying up is quite common in performance horses and especially in young fillies. Many factors have been blamed for tying up, including vitamin E and/or selenium deficiencies, electrolyte imbalances, faulty regulation of calcium levels, or a build-up of lactic acid (a by-product of anaerobic work) in muscle tissue. One idea is that, for some horses, tying up is caused by difficulty in using the carbohydrates from grain as fuel for muscles. Recent research has shown that many such horses improve markedly on a diet in which 20 to 25 percent of their energy needs are provided by fat.

Workable Amounts of Fat to Feed and the Adaptation Period

Although larger amounts of fat can be fed, most work to date indicates that the effective concentration of fat needed to achieve the effects described is an amount that will provide 18% to 20% of the digestible calories in the diet. This can be achieved by formulating a total diet (grain and forage) that provides 8% to 9% total fat. To obtain the beneficial effects described for performance horses, adequate amounts of carbohydrates must be fed in the fat supplemented diet.

Another way to provide the desired calories from fat is to add approximately 10% fat to a high carbohydrate diet, balance the diet for proper nutrient: calorie ratios and feed the diet in approximately a 65:33 ratio with hay/chaff. While higher amounts of fat can be fed to horses, any benefits of adding fat to the diet of horses in amounts that provide more than 18% to 20% of the digestible calories from fat are not evident at this time and are not practical from a management standpoint. Feeding smaller amounts of fat may be beneficial to the general health of the horse, but to achieve maximal benefits as described herein, feeding the amounts of fat described above is necessary.

Equally important in realizing the benefits from feeding a fat supplemented diet to horses is being aware that the responses described do not occur immediately following introduction of the fat supplemented diet. It occurs comparatively quickly, however, perhaps in one week. Thus, horses can be brought up gradually over a week to the amounts of dietary fat previously described. However, metabolic adaptation to the fat supplemented diet in the performance horse requires three to four weeks. Also, the training regimen during the adaptation period must include sufficient anaerobic work weekly to activate the glycolytic muscle fibres.

For more information on feeding Rice Bran Oil or fats to horses please contact Hy Gain Feeds on 1300 HYGAIN (494246) or email us.