EFFECT OF INTERMITTENT LIGHTING, LIGHT-INTENSITY AND SOURCE ON THE PERFORMANCE AND WELFARE OF BROILERS

1Broilers are currently reared under nearly continuous lighting (CL) s chedules. However, the suitability of such lighting regimens may be qu estioned in terms of performance and welfare. This paper reviews the l iterature concerning the effects of intermittent lighting (IL) schedul es on these issues. Final body weights at market age of broilers reare d under IL schedules are equal to, or even higher than, those of broil ers reared under CL schedules. However, endogenous (genotype and sex) and exogenous (dietary composition, feeder space, etc.) factors may in teract with the lighting schedule. In contrast, feed conversion is con sistently improved with IL, partly as a consequence of a more concave growth curve (initial growth depression followed by compensatory growt h). Inconsistencies in the literature concerning the effect of IL on ( abdominal) fat content and dressing yield are caused by interactions w ith other factors. However, it is clearly demonstrated that IL reduces leg abnormalities, in particular the incidence of twisted legs. Addit ional welfare benefits of IL are found in reduced physiological stress and improved eye condition. An increase in the amount of catching dam age has been observed with IL, but this may be avoided by modifying li ght management before commencement of the catching operation. The impo rtance of light is not restricted to the lighting schedule; aspects of the light quality are also important. Although the data related to li ght intensity are conflicting, it is generally recommended that an int ensity of 51ux should be provided. Whilst fluorescent light does not a ffect broiler performance adversely, its lower use of electricity comp ared with incandescent lighting does reduce input costs. More research is needed to evaluate the impact of these qualitative aspects of ligh ting on poultry welfare.