Determination of Caloric and Nitrogen Content of Excreta Voided by Birds

INTRODUCTION IN ORDER to determine the amount of energy metabolized by caged birds under various conditions as has been carried out at the University of Illinois for several years, the caloric value of the extreta voided is subtracted from the caloric value of the food consumed during periods of usually three days. The caloric values are obtained by oven-drying and then combusting samples in an adiabatic bomb calorimeter. Recently, a source of error involving a loss of energy with drying was seemingly demonstrated for the excreta of White Leghorn hens (Manoukas et al., 1964). These workers obtained highly variable but considerably lower caloric values after drying than of fresh specimens (1.2 to 20.3% less), and also found a loss of nitrogen with drying (−7.1 to 15.2%). The present report is of an investigation of this problem with wild birds. The nitrogen content of wet and dry fecal samples was determined . . .