Control of energy balance during egg production in the laying hen.

The energetic costs of egg production are considered, as is the relationship between egg production and feed intake. Hens feed during the photophase with a peak in consumption prior to the scotophase. This pattern of intake, followed by nocturnal fast, would be expected to lead to an energy deficit at night. However, much of the energy requirement of the night is met by utilization of feed stored in the upper gastrointestinal tract. It is presumed that some nocturnal energy deficit occurs and is met by changes in metabolism and endocrine balance. The hormonal involvement in these changes in avian metabolism is discussed.