INTERMITTENT LIGHTING AND BROILER PRODUCTION .1. EFFECT ON FEMALE BROILER PERFORMANCE

The effects of intermittent and nearly continuous lighting schedules on the performance of female broilers were compared in 3 experiments. A step-up program provided 23.5 h light (L):0.5 h dark (D) from 1 to 7 days, 1L:3D from 8 to 21 days, 1L:2D from 22 to 35 days and 1L:1D from 36 to 48 days. A step-down program provided nearly continuous light from 1 to 7 days, 1L:1D from 8 to 21 days, 1L:2D from 22 to 35 days 1L:3D from 36 to 48 days or 49 days. A constant intermittent lighting program provided 23L:1D from 1 to 7 days and 1L:3D from 8 to 49 days. Nearly continuous light (either 23.5L:0.5D or 23L:1D) was used as control treatment in each experiment. Depending on the imposed intermittent lighting program, equal (step-down) or heavier (step-up and 1L:3D) slaughter weights compared with continuous lighting were observed. Cumulative feed intake of chickens reared under the 1L:3D program was lower compared to chickens reared in nearly continuous lighting. In contrast, chickens provided the step-up program consumed significantly more feed compared with chickens reared in nearly continuous lighting or provided with step-down lighting program. Compared with nearly continuous lighting, cumulative feed conversion was significantly improved by imposing the 1L:3D lighting schedule while the opposite was true with the step-up lighting program. Abdominal fat pad content was only significantly increased by imposing the step-up lighting program compared with nearly continuous illumination or with step-down lighting program. When changing from continuous lighting to intermittent lighting at 7 days of age, a transient depression in feed consumption and in body weight gain was observed in all experiments. Subsequently, chickens reared in intermittent lighting manifested compensatory growth so that at the same slaughter age, equal (step-down) or heavier (step-up and 1L:3D) slaughter weights compared with continuous lighting were attained. The catch-up growth of the chickens on the step-down program and on the constant 1L:3D program was also realized with an improved feed conversion but not for chickens on the step-up program.