“Energy can not be created nor destroyed, only changed from one form to another”.
The manufactured feeds that we give to horses are generally complex mixtures of many different types of substances, such as:
a. CARBOHYDRATES - made up of simple sugars (monosaccharides) e.g. glucose, and complex sugars (polysaccharides) e.g. starch.
b. FATS - made up of fats, lipids and oils.
c. PROTEINS - made up of carbon, hydrogen, oxygen and nitrogen, which in turn are formed from ‘amino acids’ - the building blocks of proteins. There are 20 primary amino acids that make up most proteins, ten of which are essential for the horse.
In addition to these 3 major components of foods, other substances are substances are usually present, e.g.
1. VITAMINS - A, B, C, D, E,
2. ELECTROLYTES - Calcium Chloride, Potassium, and Sodium.
3. TRACE ELEMENTS - Copper, Manganese, Zinc.
4. OILS - high in Omega 3 & 6.
5. DIGESTIVE AIDS - e.g. Yea-sacc.
6. FIBRE e.g. Alfalfa, sugar beet.
Some Feed Companies, like STONEBRIDGE, also add detox substances, e.g. ‘Mycosorb’ to counteract the growing problem of mycotoxins found in feed, forage and bedding. The energy component of manufactured feeds is principally the carbohydrates and fats. It is a common misconception that high protein levels are necessary in feed for performance. The main function of protein is growth and repair. Protein is only used for energy in extreme circumstances, such as starvation. In young, growing animals its function is to build body tissues, and to re-build tissues (muscle, tendons, ligaments and bones) that are broken down during exercise and normal wear and tear in the older horse.
Digestion of fibre feed is achieved mainly through bacterial and microflora action in the hind gut, rather than in the stomach and small intestine, but the digestion of carbohydrates begins with enzymatic action in the small intestine. Because of the rapid transit of food through the stomach it is important that high carbohydrate foods are fed in small amounts to prevent high amounts of undigested carbohydrates arriving in the hind gut and causing problems. Enzymes are proteins that assist the breakdown of the nutrients in carbohydrates and fats into their basic units in order for them to be absorbed into the body. Bacterial digestion in the hindgut is a basic fermentation process, resulting in end products such as amino acids, volatile fatty acids and vitamins vital for the body’s energy functions.
However, at the level of individual cells within the body, and specifically muscle cells, it is not fats nor carbohydrates that are directly used for energy production, but a compound called ‘adenosine triphosphate’ (ATP) which is stored within all living cells in the body. The process of breaking down ATP into usable energy within the cell is called ‘metabolism’, which obtains the fuel for this process from the carbohydrates and fats.
In animals, including the horse, the stored form of carbohydrates is ‘glycogen’ which is made up of thousands of glucose molecules. This is used to regenerate ATP for muscular contraction and is a relatively rapid process, controlled by the enzyme, ’glycogen phosphorylase’, and the whole process is called ‘glycolysis.’
Fat is the other source of fuel that can be used by the horses to generate muscular contractions. Whereas glycogen can be metabolised through glycolysis, fat can only be metabolised to regenerate ATP in the muscle cells and requires oxygen. In the horse’s diet the most common form of fat is the oil that is used in the feed. The range of oils used by manufacturers includes corn oil, sunflower oil, fish oil, flax oil, oat oil, etc. Most of these oils are high in omega 3 and 6, and so have a beneficial effect on the horse’s health as well as providing energy.
It is important to remember that the horse has evolved as a forage feeder, grazing up to 16 -18hrs per day The enzymatic digestion of most proteins, sugars, starch and oils should take place in the small intestine, situated between the stomach and hind gut, but meal size will determine how long food stays in the stomach and how quickly it passes through the small intestine. Large amounts of feed pass through the stomach more quickly thereby decreasing the initial breakdown of the feed components by acidic action. Large meals pass through the small intestine more quickly reducing the breakdown of proteins, starches, oils and sugars
This means that a greater amount of these substances will reach the hindgut where fermentation takes place by bacteria. The fermentation, particularly of protein and starch in the hindgut is much less beneficial to the horse in terms of energy and amino acid supply. Also, if too much starch is fermented in the hindgut, it can contribute to serious health issues arising, such as colic, laminitis, liver and kidney problems.
What all this means is that large meals will reduce the overall nutritional uptake, because they pass through the small intestine too quickly, thereby reducing the absorption of the minerals and vitamins. It is therefore much better to feed an extra feed per day than to increase the meal size, as more energy is produced from the available food.