Metabolizable energy ( ME ) determination depends on in vivo bioassays because there is limited success of laboratory methodology to directly quantify ME in feedstuffs. In poultry, the ME values of feedstuffs are considered universal, meaning that they apply across poultry species and different physiological states. This is widely supported in the literature except for young birds, where ME is lower, which is associated with lower digestibility coefficients for nutrients. A fundamental assumption in nutrition is the independence and additivity of ME values of feedstuffs, which is confirmed in the literature and in commercial poultry production. A couple of noticeable exceptions are lipids and exogenous enzymes that can interact with feedstuffs and the animal to modify ME content. Enzymes can alter the digestibility of the main energy-containing nutrients in a diet: lipids, carbohydrates, and amino acids. Thus, enzymes can directly (e.g., amylases and proteases) or indirectly (e.g., phytase and some carbohydrases) provide extra ME to birds. Considerable variation in ME content exists within each feedstuff as indicated in some nutrient tables now including SD and CV values. Feed is the highest cost of production in poultry, and energy is undeniably the costliest component of the diet. Thus, energy is the biggest cost for poultry production. Therefore, accurate, precise, and continuous quantification of feedstuffs’ ME is critical to implement a precision nutrition approach to enhance the economic and biological efficiency of worldwide poultry production.
Escobar et al. (Fri,) studied this question.