LIGHTING AND MORTALITY-RATES IN DOMESTIC-FOWL

1. Data from intermittent and conventional lighting trials were analys ed to investigate the effect of daily illumination upon mortality duri ng the laying period and in 49-d-old broilers. 2. Liveability in layin g hens was improved by the use of intermittent lighting: the degree of improvement was proportional to the reduction in daily illumination a chieved by the intermittent programme. 3. The reduction in mortality w ith intermittent lighting in laying hens was not the result of intermi ttent lighting per se. Intermittent regimens which did not reduce dail y illumination did not reduce mortality. 4. Mortality in both conventi onally-lit laying hens and 49-d old-broiler chickens increased with ph otoperiod.