Comparison of equations for predicting the metabolisable energy intake of laying pullets.
1. The accuracy of equations to predict metabolisable energy intake of laying hens was compared using a random sample of the data set of Marsden and Morris (1987). 2. The equation of Pesti et al. (1992) was found to be significantly better at predicting metabolisable energy intake than the equations of Byerly (1941), Emmans (1974), Byerly et al. (1980), and the National Research Council (1984) when equation residual mean square errors were tested. 3. The equation of Pesti et al. (1992) had the highest coefficient of determination (R2), the smallest average residual, and smallest mean square error. The NRC equation predicted the average metabolisable energy intake best, indicating that over- and under-predictions offset each other. 4. The equations of Emmans (1974) and Pesti et al. (1992) were essentially without bias across temperature zones: less than 20, greater than = 20 less than 25, greater than = 25 less than 30, and greater than = 30 degrees C. The equation of Byerly (1941) over-predicted below 25 and above 30 degrees C, but under-predicted between 25 and 30 degrees C. The equation of Byerly et al. (1980) under-predicted below 30 degrees C while the NRC (1984) equation under-predicted above 20 degrees C.
Pesti
G M
GM
Department of Poultry Science, University of Georgia, Athens 30602.
Dorfman
J H
JH
Gonzalez
M J
MJ
D000818:Animals; D002645:Chickens / Q000502:physiology*; D002149:Energy Intake; D004734:Energy Metabolism; D005260:Female; D005544:Forecasting; D008433:Mathematics; D013696:Temperature