Artificial light sources and their influence on physical activity and energy expenditure of laying hens.

1. The influence of fluorescent and incandescent artificial lighting in a 16L:8D day/night schedule on number and intensity of movements, and on total, resting and activity-related energy expenditure was investigated. 2. Fluorescent light showed the same positive correlation between light intensity and physical activity at all activity levels as was found previously for incandescent light. 3. Light-dependent physical activity under fluorescent light was higher than under incandescent light at illuminances of 5 lux and above, indicating the fowl's ability to perceive qualitative light differences. 4. Total and activity-related energy expenditure were positively associated with illuminance; resting energy expenditure was not influenced. 5. Total, resting and activity-related energy expenditure were not statistically significantly different between light sources. 6. The results are discussed in relationship to Teichmüller's concept of adequate lighting and the characteristics of the fowl's visual system.