Factors Affecting the Metabolizable Energy Content of Poultry Feeds

GROSS, digestible, metabolizable, productive or net energy values may be used to describe the energy content of a feed. A gross energy value indicates the total amount of energy present in an ingredient but, as this bears no relationship to the amount which is actually available to the animal, such values are of no practical use in the formulation of rations. Digestible energy values vary greatly depending upon the species being fed; consequently, values obtained from studies with mammals are not necessarily applicable to poultry. The direct determination of digestible energy values for materials fed to poultry is difficult due to the problems associated with separating the feces from the urine. The determination of productive energy values is laborious while net energy determinations require very specialized equipment as well as a considerable amount of time. Metabolizable energy values are relatively simple to obtain and provide a measure of the feed …