47. Daylength and light intensity are major factors in the development of the reproductive system of the broiler breeder. The varying pattern of daylength/ light intensity in rearing and laying houses stimulates reproductive activity and egg laying. Controlled-environment houses allow the manipulation of light pattern and intensity, and breeding companies work to precise lighting programmes. When chicks are first placed the period of darkness is fairly short and light intensity levels relatively high (50-60 lux) but by the time they reach about 10 days of age they are on a constant daylength of about 8 hours in significantly lower light levels. We were concerned to note that some producers routinely kept light levels on rearing farms as low as 2-3 lux as a precautionary measure to reduce the risk of aggression. Shortly before the planned onset of lay, daylength is increased in a step-wise fashion to a maximum of about 16 or 17 hours which is held from 30 weeks of age. Light intensity during lay may be as high as 60 lux.
48. It is important for the welfare of the birds that they are kept in light at sufficient intensity that enables them to see clearly and to investigate their surroundings. Extremely dim light can cause damage to birds' eyes. Lighting systems in rearing houses should provide a minimum of 10 lux at bird eye height to encourage investigation and stimulate activity. It has long been industry practice to provide birds with a period of darkness which is important for bird welfare.
49. The proposed welfare code should incorporate information about minimum light intensities and photo-periods. Suggested figures are:
up to 10 days - minimum of 60 lux at day old, reducing to 10 lux and an uninterrupted minimum of 8 hours by 10 days of age.
up to point-of-lay - minimum of 10 lux. Uninterrupted daylength minimum of 8 hours.
laying - minimum of 20 lux. Uninterrupted daylength increasing from 8 hours to a maximum of 18 hours.
All the above should be measured at bird eye height. If aggression occurs, the lights should be dimmed for a few days.
50. After the first few days of life, there should be a set period of at least 6 continuous hours of darkness in any one 24-hour period.