Physical activity and energy expenditure of laying hens as affected by light intensity.

The influence of light intensity using incandescent bulbs in a 16L:8D day:night schedule on the number and strength of movements and on total, resting and activity-related energy expenditure was investigated. Movements were classified into 10 activity levels of progressively increasing vigour. The number of movements at all activity levels was significantly positively correlated with the logarithm of the light intensity. Movements of low activity strength were less affected by increasing light intensities than vigorous movements. Activity-related energy expenditure was highly significant and positively affected by light intensity. A decrease of the light intensity from 120 to 1 lux may reduce total energy expenditure by 18%. A decrease in energy expenditure by 9% may be achieved by reducing the light intensity to about 15 lux, measured perpendicular to the main axis of radiation.