Energy Animals require energy for maintenance, growth, work, and for the production of milk and wool. Feeds are evaluated in terms of the amount of energy an animal can obtain from them. Amount of DE needed by an animal per day varies according to body size, weight gain, milk production, and work. The amount of energy required to maintain an animal for one day without loss of body weight is called the energy required for maintenance. 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.