Prediction of metabolizable energy of broiler diets from chemical analysis

Eighty-six broiler diets were studied to develop prediction equations for true metabolizable energy (TME) with nitrogen correction (TMEn) and calculated apparent metabolizable energy (AMEn) from chemical composition. Analyses were selected according to their capacity to represent the terms used in energy calculations, namely, dietary gross energy and energy excreted relative to diet consumed. Dietary gross energy was found to be highly correlated with ether extract alone. Prediction of excreta loss improved substantially with inclusion of two terms: a measurement of fiber [either crude fiber (CF), acid detergent fiber (ADF), or neutral detergent fiber (NDF)] and ash. A composite variable based on starch plus crude protein in place of fiber and ash yielded similar predictions. Accuracy of prediction of TMEn approached that of the biological analysis, but prediction of TME was somewhat less successful. Neutral detergent fiber was less satisfactory as a predictor than ADF or CF. Calculated AMEn was also highly predictable from ether extract or diet gross energy and a measurement of fiber alone; ash apparently was less helpful for AMEn. Previously published equations based on ether extract, ash, and an estimate of fiber gave results similar to the derived equations.