It is recommended that 25 lux (2.5 foot-candles)
in the darkest part of the house, as measured
at chick height, be used during brooding to
encourage early weight gains. Optimum light
intensity at floor level should not vary by more
than 20%. After 7 days of age, or preferably at
160 grams body weight, light intensities should be
reduced gradually to 5-10 lux (0.5-1 fc).