Ultraviolet light provisioning: Preferences from the broilers’ viewpoint

The light provisioning in barns can have a great impact on broiler health and welfare. In contrast to humans, broilers are able to see ultraviolet light, and it has been suggested that UV-A light provisioning can have beneficial effects on broilers. However, it is yet unclear what broilers’ preferences regarding UV-A light are. This study investigated preferences of in total 168 fast- (Ross 308; R ) and slower-growing (Hubbard JA757; H ) broilers, distributed across 14 pens, for two light conditions: UV-A light provided ( UV ) or no UV-A light provided ( non-UV ). These light conditions were provided in replicate pens with two separate compartments (one UV and one non-UV) that the birds could freely move between. From hatching until slaughter age, it was studied 1) where broilers chose to be, 2) what behaviours were performed in the two light conditions, and 3) how much feed was consumed in the two light conditions. Across the day (05.00–23.00 h), both breeds appeared to show a preference for the UV light condition in the first weeks of life but later in life no clear preferences were observed. In the evening (19.00–23.00 h), R birds did not show a clear preference, whereas H birds showed a preference for UV in the first four weeks and a preference for non-UV light in weeks 6–8. Regarding behaviour, more drinking behaviour was observed in the UV condition compared to the non-UV condition in both breeds and more foraging behaviour was observed in H birds in the non-UV light condition than H birds in UV or R birds in either light condition. Furthermore, higher average daily feed intakes were observed on the UV side than on the non-UV side, during the starter feed phase for both breeds and during the finisher feed phase for R birds. Overall, apart from the first weeks, no preference for – or avoidance of – the UV light was observed during the day, but there was a shift in preference from UV to non-UV light in the evening over time for H birds. Furthermore, there were few preferences related to behaviour, but there was an indication for a higher feed intake under UV light conditions. The results of this study emphasize the importance of offering varied light conditions to broilers, so the birds can select their preferred light condition at a given time. • Broilers’ preferences for UV light provisioning were studied. • Preferences for UV light vary by time of day and age of the birds. • Slower-growing broilers show stronger UV light preferences in the evening. • Higher feed intake levels were observed in the UV light condition.