Ultraviolet light preferences in a white and a brown layer pullet strain.

Adequate lighting in laying hen houses is of great importance for hens' health, welfare and performance. One light aspect that is present in the natural environment of chickens is ultraviolet (UV) light, and several studies have suggested that addition of UVA light might have positive effects on laying hens' welfare. In this study we investigated the preference of layer pullets of two breeds - Lohmann LSL Classic (white; W) and Lohmann Brown Classic (B) - for two levels of UVA light, and assessed 1) under which light condition (low UVA level (low-UV) versus a higher UVA level (high-UV) light) they spent most time and 2) what behaviors were performed in the different light conditions. A total of 132 W and 126 B birds were housed in pens (21-22 birds per pen) that were divided in two equal areas with the same light intensity (± 100 lux) but with different UVA levels (low-UV versus high-UV). Video recordings were made from above the pens and birds were automatically counted on each side using a computer vision detection algorithm. Behavior was observed at pen level using instantaneous scan sampling at 1, 2, 4, 6, 8 and 10 weeks of age. For the daytime period, it was observed that W birds had a preference for high-UV in the first three weeks of life, while no clear preferences were observed in B birds. In the last hour before lights off and the first hour of the dark period, B showed a preference for low-UV in week 2 and no clear preference at later ages, while W birds did not show a clear preference at the end of the day at any age. No differences between the low-UV and high-UV light condition were observed in the proportion of behaviors performed in each. These findings suggest that there might not be an exclusive preference for either low-UV or high-UV.