Effects of artificial dusk lighting on perching behaviors of cage-free laying hens

Abstract. Perching is chickens' essential natural behavior and is regarded as anti-predatory behavior in wildfowl and laying hens. Laying hens show higher perching behavior (PB) during nighttime. In commercial cage-free (CF) houses, chickens' PBs, such as perching frequency, time, and height, are affected by lighting management (e.g., light intensity, period, and color). For instance, dimmable light is recommended to enhance perching performance and reduce damages caused by failed perching. This research was conducted to test whether dusk lighting (DL) systems significantly affect PB. The objectives of this study were to 1) assess the effect of an artificial DL system on PB of CF laying hens; and identify the effect of the DL systems on perching height during nighttime. A total of 720 Hy-line W-36 laying hens in four identical rooms (180 birds/room) were investigated. The hens were provided with A-shaped perch totaling 36.6 meters (0.2 meter/hen). Each room had the same lighting programs during the daytime, while a dimmer programmed the DL period. Treatment rooms were randomly assigned with 4 different DL durations of 0, 15, 30, and 60 minutes based on the Latin Square Design method. The PB data were collected twice a week after the light turn-off from 37 to 57 weeks of age (WOA) at different heights (H1=1.2ft; H2=2.2ft; H3=3.1ft; H4=4.1ft; H5=5.0; H6=5.8 from the litter floor). Hens' PB at different heights and between treatments were analyzed using ANOVA in R studio 4.2.1, and the means were separated using the Tukey HSD method (p<0.05). The results show a significant increase in PB with the DL system (p<0.05). The DL period of 30 minutes resulted in the highest PB compared to other treatments. When comparing heights, the highest height was preferred to the lowest (p<0.05), and PB decreased as perch height decreased. Our findings will provide a basis for improving laying hen behavior and welfare in CF facilities.