Impact of natural and artificial light treatments on fear response and welfare parameters in commercial broilers

Abstract

In recent years, there has been a movement driven by consumer demands towards adding windows in broilers house to allow for natural light (NL) during rearing; however, little is currently known about the effects of NL on bird behavior and welfare. The objective of this study was to compare the impact of raising broilers under NL or artificial light (AL) on fear response and welfare parameters. Mixed-sex Ross 708 chicks (N=720) were housed in 16 rooms (44 birds/room), with 8 rooms per light treatment and raised until 55 days of age. Chicks were randomly assigned to one of two light treatments: artificial light provided via a 5000K LED or natural light provided via 1 ft2 window and 5000k LED. Fear response was measured on days 14 and 35, by the novel object (NO) and response to observer tests. In the NO test, the latency to first interaction with NO, latency to approach NO, and the number of birds approaching the NO within a 1-meter radius was recorded at 30-second intervals for a duration of 5 minutes. In the response to observer test, the number of birds that moved away in response to the pen door opening was measured. On day 55, welfare parameters such as hock burn, foot pad dermatitis, gait score and latency to lie were assessed. Data were log transformed for normality. The effect of light treatment was analyzed using a paired t-test in R (version 4.0.2). A p-value of <0.05 was considered statistically significant, and a p-value of ≤ 0.1 indicated a tendency toward significance. No difference was found between treatments for hock burn, gait score, latency to first interaction with NO, latency to lie, and the response to the observer test on day 14. In fear response assessments at 35 days, the number of AL birds (M=0.46) that approached the NO was significantly lower than that of birds raised in NL (M=1.74; p<0.001; t=6.78). At 35 days of age, chickens raised with NL had a shorter latency to approach NO (3.92s) than those raised with AL (5.40s; t=-3.21; p<0.01). On the 35 day, there was a tendency towards significance for birds raised with NL to move away from the observer more frequently compared to those raised with AL. Furthermore, another tendency was observed where NL chickens showed a higher interest to explore NO compared to AL chickens on the 14 day of age. Moreover, birds raised with NL (M=0.2) showed significantly lower foot pad dermatitis scores when compared with the birds raised with AL (M=0.6; p=0.01; t=-2.85). Overall, this study shows that the provision of NL could improve foot health and reduce fearfulness in broilers.