An evaluation of the true metabolizable energy assay for monitoring the apparent metabolizable energy values of poultry diets.

Samples of 35 diets were obtained from five different regions of Canada. The true metabolizable energy (TME) of these diets was measured with mature White Leghorn cockerels. The N-corrected apparent metabolizable energy (MEn) values, calculated from average analysis figures, were supplied by the feed manufacturers. The relationship between TME and MEn was examined in two ways. First, the MEn values were multiplied by 1.097, the factor to convert MEn to TME derived by Sibbald (1977), and the results were compared with the corresponding determined TME values. The percent difference between the estimated and determined TME values were for Alberta from -7.1 to 3.1; for Manitoba from -9.8 to 5.4; for the Maritimes for -.3 to 10.8; for Ontario from -3.9 to 14.7, and for Saskatchewan from -4.2 to 5.7. Second, the ratio of determined TME:MEn for the various diets was calculated. The ratios varied considerably both within a region and between regions, ranging for Alberta from 1.063 to 1.176; for Manitoba from 1.041 to 1.204; for the Maritimes for .990 to 1.102; for Ontario from .957 to 1.141, and for Saskatchewan from 1.036 to 1.144. These data suggest that the TME assay could not be used to accurately monitor the MEn content of diets in commercial practice. However, this may have been due to imprecision in the TME data or in the MEn values or both.