Impact of natural and artificial light treatments on welfare and behavior in commercial broilers

Abstract

In recent years, consumer driven interest has led to the addition of windows in broiler houses to allow for natural light during rearing. However, the effects of natural light on broiler welfare and behavior remain largely unknown. This project aimed to evaluate the impact of natural light (NL) versus artificial light (AL) on broiler fear responses, welfare indicators, behavior, and spatial distribution throughout a 56-day grow-out period. A total of 704 mixed-sex Ross 708 chicks were randomly assigned to 16 rooms (44 birds/room), with 8 rooms per light treatment: AL provided via 5000K LED lighting, or NL delivered through windows supplemented with 5000K LED. Three fear tests were performed – novel object (at 14 and 35 days), response to observer (at 14 and 35 days), and novel environment (at 55 days), alongside welfare assessments including footpad dermatitis, hock burn, gait score, and latency to lie at 55 days. Behavioral observations were conducted via scan sampling every 30 minutes over a 24-hour period on days 5, 12, 33, and 54. Behavioral observations and birds’ distribution were conducted for 8 rooms total (4 per treatment group). Bird distribution in NL rooms was evaluated by counting the number of birds on sunlit versus shaded sides during the photophase. Fear response and welfare data were analyzed using PROC MIXED or PROC GLIMMIX, while behavioral and distribution data were analyzed using repeated measures PROC GLIMMIX (SAS 9.4). Results indicated that NL birds were quicker to approach the novel object (mean latency 69.9 s vs. 181.4 s, P<0.01) and were more willing to enter the 1-meter zone around the object (P=0.03), though no treatment differences were observed in the response to observer, novel environment tests, or most welfare parameters, except for footpad dermatitis, which was lower in NL birds (P=0.03). For behavioral observation, an interaction was noted for walking and sitting. Treatment has an effect as NL birds performed more walking and other locomotion activities (P<0.05), while AL birds showed more sitting behavior (P<0.05). Age significantly influenced all behavioral categories except running, environmental pecking and frolicking. Additionally, birds preferred the sunlit side over the shaded side in NL rooms (P<0.05). Overall, natural light exposure promoted more active behaviors and improved some welfare indicators such as footpad health but did not significantly affect leg health or fear responses.