Ultraviolet light and mating behaviour in domestic broiler breeders

1. The perception of UVA light (320<<lambda><400 nm) by domestic fowl may b e an adaptation to naturally lit habitats and may still be functional in fa rmed varieties, although not utilised owing to the absence of these wavelen gths in commercial house lighting. One function may be the mediation of sex ually related signalling or communication. 2. In experiment 1, two groups of 41 adult broiler breeders (four cockerels , 37 hens) were kept under conventional fluorescent light, with or without fluorescent UVA supplementation amounting to 16.9% of the total spectral po wer output of the luminaires. Each light environment was approximately iso- illuminant as perceived by the birds. The two groups were exposed to the li ght environments alternately for five 2-day periods in a cross-over design. Mating behaviour, production measures and time budgets were recorded on th e second day of each period. 3. A UVA-enriched environment increased the number of attempted matings (1. 27 vs 0.99 matings/cockerel.h) and locomotion (5.3 vs 3.7 min/bird.hour). 4. In a second experiment, 10 hens were allowed to choose between four cock erels lit under different power levels of UVA (1.6%, 14.6%, 43.5%, 57.5% of the total spectral power output of the luminaires) in a four-armed maze. A gain, each light environment was approximately iso-illuminant as perceived by the birds. Each hen was allowed to make one choice per day over four day s, with the position of the cockerels and the UVA levels interchanged each day. This schedule was repeated with the same hens for two other groups of four cockerels. 5. At a distance of no less than 60 cm from the cockerel, the hens spent mo st time inspecting whichever cockerel was lit by 1.6% or 14.6% UVA (1.33 vs 1.37 vs 1.22 vs 1.16 log seconds/hen.choice, respectively for increasing U VA level). Similarly, when allowed to approach closer to the cockerels, the hens spent most time in the arm which contained a cockerel lit by 14.6% UV A light, (1.62 vs 1.88 vs 1.69 vs 1.51 log s/hen.choice, respectively for i ncreasing UVA level). 6. UVA is clearly implicated in the transmission of sexual signals or commu nication which may have implications for the welfare and production of broi ler breeders.