Energy utilization by laying hens. I. Energetic efficiencies of maintenance and production

The energetic efficiency of metabolizable energy conversion to net energy for maintenance and/or production was determined in laying hens. The techniques employed indicated that maintenance and production had essentially the same efficiencies (.619 and .628, respectively). Fasting heat production was 69.28 kcal/Wkg75 (physiological body weight) and the maintenance requirement was 111.1 kcal/Wkg75. Limiting metabolizable energy intake in laying hens reduced both egg weight and hen-day production. Regression equations predicted a reduction of 1.53 g in egg weight and a reduction of 2.5% in egg production for each 10 kcal metabolizable energy reduction in intake. This paper reports techniques which may be employed for energetic efficiency evaluations of feedstuffs, mixed diets, and energy utilization by laying hens in short term studies.