Modelling for the estimation of the metabolic energy requirement of laying chickens

Experiments were conducted to assess the degree of accuracy with which the Metabolizable Energy (M.E.) requirements of laying chickens in production could be predicted. Three of the most recently published prediction models (Emmans 1974, McDonald 1978, and NRC 1981) were evaluated using production data covering a full laying cycle. While each model proved valid under certain environmental, physiological and productive conditions, none was valid over the full production period. A new equation was developed as a derivation of the NRC (1981) equation. ME = 128 W[sup 0.75]* 1.015[sup (25-T)] + 5.50 G + (2.07 * 1.03 [sup (E-62))* (E*R) WHERE: ME = METABOL IZABLE ENERGY, KCAL/DAY W = BODY WEIGHT, KG G = BODY WEIGHT GAIN/LOSS /DAY, GM E = EGG WEIGHT, GM R = 7. RATE OF LAY / 100 T = AMBIENT TEMPERATURE, ° C A factor was included in this new equation to account for the differences in egg component yeild relative to egg weight. This new equation was evaluated against the same full cycle production data as were the Emmans', McDonald and NRC equations and was found to be able to predict M.E. intake with greater accuracy. All four prediction models (Emmans 1974, McDonald 1978, NRC 1981 and Dornan) were then further evaluated using three individual sets of experimental flock production data. The Dornan equation, in all cases, was found to be superior in its ability to predict Metabolizable Energy intake of laying chickens in production.Land and Food Systems, Faculty ofGraduat