Effects of increasing photoperiod length on performance and health of broiler chickens

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Abstract
1. Broiler performance and health were compared from 0 to 42 d for lighting programmes consisting of near‐continuous light 23L:1D (23L), a lighting programme where photoperiod gradually increased from 6 to 23 h between days 4 and 35 (INC) or an increasing‐lighting programme with 1 h of light mid‐way through the scotophase (INC+1). 2. The increasing lighting programmes reduced growth rate and increased gain: food ratio from 0 to 21 d; INC + 1 growth rate was intermediate to the 23 L and INC treatments. From 0 to 42 d there were no differences in growth rate or gain:food ratio among lighting treatments. Males grew faster, ate more food and converted food more efficiently than females. 3. The increasing‐lighting programmes (INC and INC+1) resulted in less skeletal disease than the 23L control. The incidence of sudden death syndrome (SDS) and mortality other than SDS were numerically lower for the increasing lighting treatments. More males died as a result of SDS and were affected by skeletal defects than females. 4. In terms of health, increasing lighting programmes were superior to near‐continuous light for broiler chickens.