The objective of this research programme was first to examine the effects of light colour on the behaviour and performance of broilers and to see whether this could be utilised to alleviate leg disorders. Secondly, the research programme investigated the birds' preference for different colours and the interactions between colour and intensity in the birds' perception.
Under 30 lux intensity of light, the birds were found to be more active in red and less active in blue and green light. Birds in white light were in between red and blue or green. The greater activity occurred under red light, while birds in the blue or green light seemed more inclined to sit passively and doze. Broilers reared under different colours of lighting exhibited similar growth but developed more skin compared to broilers reared under white light. The heaviest gut contents were found in birds under blue light and the lightest were under red light. Both male and female broilers showed the greatest longterm preference for blue light, followed by green light, although their initial preference after the neutral colour was for red light. Birds reared in a coloured light showed an initial preference to remain in that light but after one week had elapsed, they preferred a change to a different colour, usually blue.
The chickens failed to differentiate the brightness of blue and red lights at a (photon) ratio of 3.1 - 3.6 : 1.0. Birds were reared under red and blue lights in equated brightness at three intensities, low (12xl020 photons and 36x1020 photons for red and blue lights respectively), medium (18xl020 and 60xl020 photons for red and blue) and high (30xl020 and 108xl020). The results showed that the time spent feeding and sleeping and the quantity of pecking, wing stretching and aggression were increased in red light, whilst birds in blue light increased their time spent standing, sitting and dozing. As the light intensity increased, feeding, walking, wing stretching and aggression tended to increase, particularly for birds reared in red light. No interactions between colour of light and intensity were found for the time spent feeding and sitting but they were for other behavioural parameters. Again, the treatments did not affect growth rate, feed consumption and conversion ratio.
During the rearing period three colour light patterns, [dim blue light from day 1 to 49 as a control(TO); red light from day 1-16 followed by dim blue from day 17- 49(T1) and dim blue from day 1-16 followed by red at day 17-32 and blue from day 32- 49(T2)] were applied to examine the effects on the behavioural and physiological responses of broilers. The red and blue light were of intensity 860xl020 and 1.5xl020 photons respectively, and were produced from white light covered by filters. Standing time during the life of the birds was not affected by treatment, but using bright red light increased the time spent walking, stretching and feeding, particularly when applied in the first 16 days. The heaviest final body weight and highest feed efficiency were obtained in T1 although, there was a tendency for an increase in feed consumption in TO. In addition, the treatment did have an effect on bone strength, causing a reduction in the bone strength of birds in T2. The sex of the birds did not affect their behaviour or response to light. Similarly, tibia strength was not affected by sex and neither were
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differences between left and right leg. The use of continuous blue light gave rise to the highest incidence of lameness problems.
It is concluded that, first, the birds are more active in red and less active in blue and green light. Second, giving bright red light in early life increased the time spent walking, stretching, and feeding, which allowed young chicks to exercise sufficiently. As a result, it tended to increase bone strength and alleviated lameness problems. However it reduced bone strength when applied later in life. Broilers reared under different colours of lighting had more skin compared to broilers reared under white light. The heaviest gut contents were found in birds under blue light and the lightest were obtained under red light. Third, both male and female broilers show the greatest longterm preference for blue light, followed by green light, although their initial preference, after a neutral colour, is for red light. Birds reared in a coloured light show an initial preference to remain in that light but after one week prefer a change to a different colour. Fourth, in the equated brightness of red to blue at a ratio of circa 1.0 : 3.3, there were distinct effects of colour of lighting on broiler behaviour with increased activity in red light. Increased intensity also stimulated behavioural activity, particularly in red light.