The degree to which a lighting program will effect broiler production is influenced by a number of factors: • The time of program implementation: early implementation being most effective in benefiting bird health. • Age at processing: older birds being likely to benefit more from darkness exposure. • Environment: the effects of increased stocking density (above recommended levels) will be made worse by longer darkness exposure, but adjustments such as the use of dawn to dusk systems will help alleviate these issues. • Feeder management: the effects of limited feeder space will be made worse by longer darkness exposure, but again, proper management of lighting programs (i.e. dawn and dusk systems) can help alleviate the problem. • Rate of bird growth: the impact of lighting will be greater in rapidly growing birds.