Effects of the Nitrogen Correction and of Feed Intake on True Metabolizable Energy Values

An experiment was conducted to measure the effect of correcting true metabolizable energy (TME) estimates to zero nitrogen balance (TMEn) and to examine the effect of feed input on TME and TMEn values. There were 96 adult cockerels in a randomized block design comprising 16 treatments and 6 replications. The treatments were an unfed negative control and five feedingstuffs each at three levels of input. The experiment followed the basic procedures of a TME assay, but the excreta collection period was extended to 72 hr because some birds had impacted crops. None of the regressions of excreta energy on feed input level departed from linearity (P>.05). Intercepts on the zero input axis were lower than the estimate of metabolic + endogenous energy (FmE + UeE) loss made with unfed birds. Although the differences, which ranged from 6.5 kJ for oats to 30.5 kJ for fish meal, were not significant (SE 22.6; P>.05), the result was that TME values estimated using the FmE + UeE values for unfed birds decreased slightly as feed inputs increased. The nitrogen correction reduced the energy loss of unfed birds from 127.3 to 56.0 kJ/bird/72 hr and the error mean square by 40%. The TMEn estimates were slightly smaller than TME values and were independent of the level of feed input.