LIGHTING LAYERS Intensity In natural light (window) housing the natural light is supplemented with 1.5 - 5.0 fc for the period when supplemental lighting is used. It has been found that birds exposed to very dim lights, say 3 hrs at.02 -.03 fc) prior to exposure to bright lights, say 8 hrs at .5 fc or more, might perceive this as sunrise and daylight and shift their biological clock as if exposed to 11 hours of normal light. However, the reverse, dim following bright, does not shift their perception. It appears that the threshold intensity for photostimulation is about .15 fc. However maximal egg production has been achieved at intensities between .5 and 1 fc. Lux A lux of light intensity is equal to one lumen per square foot. 1 foot candle = 10.76 lux Duration The next important aspect is duration of light stimulation. Two rules exist for this. Never Increase the duration or intensity of light during the growing period. Never Decrease the duration or intensity of light during the production period. Duration depends upon the age of the chicken and type of housing you use. Chicks can be exposed to 21-23 hrs of continuous light at one and two days of age and then reduced to 15 or 16 hrs of light until the birds are three weeks of age. (Chicks have a very low fear response during their first three days of life and can be exposed to many environmental stimuli, such as new housing, light and dark, etc. without much adverse effect.) At three weeks of age, reduce the hours of light to 10-12 hours or as dictated by natural day length. In summer for open housing use decreasing hours of light up to six weeks of age and then hold constant to avoid delays in maturity. When target body weights are achieved start your stimulatory lighting program. Jump to 13 hours and then add 15-30 min per week until 16 hrs of light is reached. Light stimulation should continue until peak production is achieved.