Responses of broilers to the near-continuous lighting, constant 16-h lighting, and constant 16-h lighting with a 2-h night interruption

Manipulation of lighting regimens is an effective way to improve the broiler production. The growing health and welfare concern for the livestock animals has raised new requirements for lighting management. In the present study, the overall responses including growth, carcass composition characteristics, health and welfare, and behavior of broilers to 3 lighting regimens (near-continuous lighting (23 h light (L):1 h darkness (D)), constant 16-h lighting (16L:8D), and constant 16-h lighting with a 2-h night interruption (16L:2D:2L:4D) were estimated, aiming at providing an optimal regimen required for both good welfare and production. A total of 360 day-old male broiler chicks (Cobb 500) obtained from a commercial hatchery were used. The chicks were randomly divided into 3 treatments, which were replicated for 4 times. The 3 lighting regimens aforementioned were initiated on d 8 and ended on d 42. For the whole study period (d 0-42), the feed conversion ratios of broilers under 16L:8D and 16L:2D:2L:4D did not differ, while the broiler chickens under 16L:2D:2L:4D had higher feed intake and BW gain (P < 0.05). The broiler chickens under 16L:2D:2L:4D had similar feed intake as those under 23L:1D, while the BW gain was higher (P < 0.05) and the feed conversion ratio was lower (P < 0.05). Slaughtered on d 42, the breast muscle yield of broiler chickens under 16L:2D:2L:4D was similar to those under 23L:1D, but higher than those under 16L:8D (P < 0.05). The abdominal fat weight of broiler chickens under 16L:2D:2L:4D was similar to those under 23L:1D, but lower than those under 16L:8D (P < 0.05). The eyeball weight and size of broilers under 16L:2D:2L:4D were smaller than those under 23L:1D (P < 0.05). As a contributor of feeling of well-being, the serum serotonin level did not differ for the broiler chickens from the 3 lighting regimens. The serum melatonin of broilers under the 16L:8D was higher than other 2 regimens (P < 0.05). Behavior observation on d 30 indicated that the broiler chickens under the 23L:1D regimen spent more time feeding than those under 16L:8D, but exhibited comfort behaviors less extensively than other 2 regimens (P < 0.05). It was concluded from this study that the 16L:2D:2L:4D regimen improved the growth, feed efficiency, carcass composition characteristics, ocular and leg health and welfare of male Cobb broilers due to the dark period and a 2-h night interruption.