Light spectrum and intensity preferences of fast- and slower-growing broilers vary by age, behaviour and time of day

Abstract

Light is an important management factor in broiler production. However, our knowledge of broiler preferences for different lighting conditions is limited, especially regarding changes in preference with age, across breeds with different growth rates and for different behaviours. Here we investigated preferences of fast- (Ross 308; R) and slower-growing (Hubbard JA757; H) broilers for a combination of light spectra (sky blue (S) and green (G) light) and intensities (15 and 100 lux), examining over time 1) where broilers chose to spend most time, 2) what behaviours were performed, and 3) the feed intake of the birds. A choice test setup was applied, where broilers were housed in replicate pens with four compartments that they could freely move between, with the four light conditions (15S, 15G, 100S and 100G) provided in the separate compartments. The birds’ locations were scored every five minutes, two days a week, using an automated computer vision approach. Behaviour was observed through instantaneous scan sampling at five ages per breed and feed intake was recorded per compartment approximately every week. It was observed that broilers initially spent most of the daytime in bright, G light (week 1), before a preference for bright, S light came up (weeks 2–3 for R broilers, week 2 for H broilers) and then no clear preference was visible for weeks 4–6 for R and 3–6 for H broilers. For H broilers, a preference for low intensity light was shown in weeks 7–8 with no clear preference for G or S light. We observed differences in the proportions of behaviours shown in the light treatments, with more inactive behaviour in dimmer and S light conditions and more active behaviours in brighter and/or G light conditions. Furthermore, there was an initial higher feed intake in 100G for R birds, and a higher feed intake in 100S than in 15S later on. For H birds, there was a higher feed intake at 15 lux than at 100 lux (for both spectra) at the end of the production period. Overall, the outcomes of this study highlight that broiler preferences for specific light conditions differ between breeds, ages and for different behaviours. These outcomes can inform the development of functional lighting programs for fast- and slower-growing broilers and suggest that providing broilers with variation in light conditions in space and time may better suit the birds’ behavioural needs and preferences, hereby potentially improving broiler welfare.