Ever wondered where do fats and oils go once they are absorbed from the small intestine? The absorption process is not an accident, nor is it a passive process, it is actually a 'forced' process.
Blood flow through the intestinal mesentery picks up the long chained fatty acid as triglycerides and these are then transported and passed through the liver before the liver decides what to do with them. (This contradicts the much passed myth that feeding oils or fats to your horse gives it diahorrea or other digestive upsets), the oil does not in fact reach the large intestine, it has been absorbed and processed long before.
If the body needs energy for muscle contraction, then it (the liver) sends the fat to the muscle where it is further broken down into two carbon units (glycogen) that are used for energy to contract the muscle cell. If the body does not need the fat at the time, then it gets stored as adipose tissue (body fat) that is found throughout the body. (This is apparent more in some bodies than others and is directly related to other hormone activity particularly pancreas and insulin responses).
Horses take time to adapt their digestive and metabolic processes to a higher fat diet. It takes anywhere between 14 - 30 days to fully adapt their digestive system and a minimum of 30 days to 'switch on' the metabolic processes in the muscle to utilize fat as an energy source (glycogen) in preference to glucose. It takes 3 - 4 months for the optimum development of aerobic energy production in the muscle so you can see that you won't get the full benefit of a high fat diet as a full on energy source over night. You will however notice within this time frame that the horse will improve in condition, particularly in coat health and appearance.
Another source of fat utilized by the horse are volatile fatty acids (VFAs), which are produced through fiber digestion by the microbial action in the caecum and large intestine. These fatty acids are constantly being produced and are the horse's main energy supply.
The VFAs are very short chain fatty acids (two to four carbons) and are handled a little differently by the body than added dietary fat. One of the VFAs, propionic acid, is a unique fatty acid in that it can be converted to glucose in the liver. The other main VFAs, acetic and butyric acid can be used for energy or stored in the adipose tissue.
Grains are high in Omega 6 whereas grasses and forages such as hay are high in omega 3. Different vegetable oils also have different Omega 3 content. Linseed and fish oils are highest but are less palatable and it is hard to feed high levels as an energy supplement. Canola is palatable oil with a good balance of omega 3 to 6 so it is very useful oil. Corn oil is very widely used but is low in omega 3 and high in omega 6. Oils high in omega 6 linoleic acid such as corn, sunflower and safflower oil will do the best job of coat conditioning. Remember that the main reason for feeding oils is for energy so don't only pay attention to the omega 3 issue as we don't fully understand the implications in horses yet.
Anaerobic metabolism does not require oxygen and can produce energy very quickly but is a far less efficient process. That means that if the horse needs quick energy for sprints or short bursts of speed, it will not be burning fat, but rather glucose from glycogen stores in the liver and muscle or blood glucose. Glycogen stores in the body are limited; on the other hand, fat stores are enormous (depending on the amount of adipose in the body). So for aerobic work, the supplies are virtually unlimited as long as the body has some stores of glycogen or glucose ("fat burns in a flame of carbohydrate"). Long distance slow work such as trail and endurance riding depends mostly on aerobic metabolism.
Fat is necessary in the horse's diet for the absorption of the fat soluble vitamins A, D, E and K and as a source of the essential fatty acid linoleic acid. Omega 3 intake in horses that are intensively exercising and those with chronic inflammatory disorders such as Queensland Itch (which is caused incidentally only by the biting midge, regardless of all the other stories and myths surrounding the cause), other allergic skin conditions, arthritis, allergic lung disorders and recurrent laminitis. This anti-inflammatory effect may not cure the problem but will reduce the severity or allow a reduced dose of anti-inflammatory medications, provided the Omega 3 and Omega 6 essential fatty acids (EFAs) are in correct balance with each other in order for them to be allowed to kick in these anti-inflammatory properties.
I have devised a blend of oils using Soybean oil and Canola oil with added Vitamin E, and WITH elevated levels of Omega 3 and Omega 6 EFAs, called EQUI-SHINE E, and have had resounding success with this product when fed in conjunction with COMPLEAT range of feeds that are well balanced and designed for a horse's digestive system in main in not only providing higher levels of safe and cool energy, but with the alleviation of Queensland Itch in particular, in many horses.
The main reasons for adding fat to the horse's diet would be to gain body condition, improve hair coat, increase energy density of the diet, and improve performance. Performance related benefits include lower lactic acid accumulation, thereby reducing the severity of tying up and further muscle damage and better behavior than when on a high grain or other high energy feed.
An increase in the amount of fat in the diet has been found to increase the amount of oil in the skin of the horse. This increase in oil in the skin will lead to a shiny, sleek, healthier-looking coat in 4 to 5 weeks. Traditionally, linseed has been fed because it was found to give the horse a nice coat and this was because of the high fat content of linseed (30%). However unless linseed is boiled it can release toxic cyanide which could kill the horse.
Similar effects have been seen with the addition of almost any source of fat. Improvements have also been noted in hoof quality from the addition of fat to the diet.
Fat is more energy dense than any other horse feed. It is about two and half times as dense as corn and three times as oats. For example, one cup of oil will provide the same amount of energy as kg of oats or a biscuit of good hay. Horses in heavy training have a very high daily energy requirement and these horses often cannot or will not eat enough feed to meet their energy needs. This results in a steady decrease in body condition and reduced performance.
In these instances, adding fat increases the energy density of the diet so that less feed and less grain is required to maintain body weight. The same situation applies if a gain in condition is required in a spelling horse, show horse or sales yearling. Adding fat to the diet can speed up the 'fattening' process or importantly reduce the amount of grain you need to feed. High grain intakes can lead to digestive disturbances, colic, laminitis, hind gut acidosis and a number of other undesirable side effects.
When the body is burning fat, it produces less heat than when burning other sources of energy, such as starch or fiber. Contrary to the popular belief that fat is a "hot" feed; it is actually very useful in hot weather. It does not heat up the body internally as much during times when the horse is already having to deal with external heat that reduce it's ability to cool itself. For example, horses at the 1996 Olympic Games were being fed as much as four cups of oil per day to help them perform in the mid-summer Atlanta heat and humidity. This amount of oil is not to be fed to horses unless the Vitamin E levels are increased accordingly. Vitamin E is a necessary vitamin and plays an important role as an anti-oxidant in the horse at cellular level, ridding the horse's tissue cell of unwanted or damaged portions and allowing it to rejuvenate.
Replacing the major portion of starch in the horse's diet with fat is becoming popular as a treatment for horses with muscular problems such as tying-up. The type of muscle problem where high fat diets have been the most successful are in horses with equine polysaccharide storage myopathy (EPSSM). These horses have a problem with storing amounts of muscle glycogen and respond well to decreasing the amount of starch in the diet and replacing the needed energy with fat. Research at KER has shown that horses prone to tying up had lower muscle enzyme levels after work when fed a high fat rather than high grain (carbohydrate) feed.
If fat is added as oil you need to feed half a cup per day to get the coat benefit and at least a cup to get a significant boost to energy supplies and utilization. This amount of oil needed will be reduced if other high fat feeds are fed such as sunflower seeds or rice bran. Up to 4 cups of oil can be fed per day but this is best divided into 4 feeds and introduced slowly, and the Vitamin E level of the ration is increased.
Feeding vegetable oil has repeatedly been proven to greatly improve coat condition, overall health and vitality, body condition, performance levels and help in the alleviation of many common skin complaints and conditions.