Variability in Metabolic Plus Endogenous Energy Losses of Adult Cockerels and in the True Metabolizable Energy Values and Rates of Passage of Dehydrated Alfalfa

An experiment with four groups of 12 adult cockerels allowed true metabolizable energy (TME) to be estimated in several ways. The birds were alternately fed one of two samples of dehydrated alfalfa meal or starved to serve as a negative control for the measurement of metabolic and endogenous energy loss (FEm + UEe). Each bird was fed twice and served as a control twice. The correction for FEm + UEe, therefore, could be estimated from the same bird, at a different period, or from a different bird at the same period. The FEm + UEe was largely characteristic of the bird. The correlation of the first observation with the second observation for each bird was .744 (44 DF). Variation in body weight did little to explain variation in FEm + UEe (r = .069, 90 DF). The most precise TME estimates were obtained by using each bird as its own negative control. A group mean value for FEm + UEe was somewhat inferior but the decrease in precision may be offset by reduced time and cost. The TME values provided additional evidence that the FEm + UEe output is characteristic of the bird. Although some birds consistently voided alfalfa residues more slowly than other birds, the pattern was not sufficiently consistent between birds to be significant.