The excreta energy and nitrogen losses of adult cockerels during a fast.

Sixteen adult Single Comb White Leghorn (SCWL) cockerels were fasted for 48 hr and then placed on an experiment during which they were fasted for an additional 11 days; water was freely available. Excreta energy (FE + UE), excreta nitrogen (FN + UN), and excreta energy corrected to zero nitrogen balance (FEn + UEn) losses were measured at 24-hr intervals as were body weights (BW) and weight losses (delta BW). One bird died on the second day of the experiment. There were significant differences (P less than .01) in excreta losses among birds and days. The day effect was curvilinear and decreasing, with the largest day-to-day changes tending to occur early in the experiment. The BW, delta BW, and ambient temperature had little effect on the losses with the exception of (FN + UN) which varied in part with BW. The regression of FE + UE on FN + UN, after adjusting for birds and days, yielded a slope estimate of 33.54 +/- 5.12 kJ/g (8.02 +/- 1.22 kcal/g) of nitrogen which is not different (P greater than .05) from values commonly used to corrected bio-available energy values to zero nitrogen balance.