The more severe the energy deficiency, the more noticeable are the symptoms described. Excess energy is stored as fat. Table 1 gives the digestible energy values of some common feeds. The most common energy source is from the carbohydrates contained in feeds. These are the sugars, starches, cellulose and hemicellulose which have been stored in plant tissues.
Lipids are another energy source found in plants.
They are fats and compounds closely related to them. They contain about two and a half times as much energy as carbohydrates. Proteins Proteins are composed of amino acids which contain carbohydrates, nitrogen and sometimes sulphur. Ten amino acids are essential to monogastrics, whereas ruminants only need a source of nitrogen, or a poor quality protein, from which the microbes in the rumen can then construct the essential amino acids. Protein is absolutely essential for growth, reproduction and maintenance in monogastrics and ruminants.