Intermittent Lighting for Laying Fowls: A Review

SummaryThe various intermittent lighting patterns described in the literature are defined and categorized.With symmetrical or repeating intermittent patterns, age at sexual maturity is shown to be delayed or unaffected, depending upon light pattern used. During lay a consistent feature is a desynchronization of ovipositions. Egg production is generally depressed together with improvements in egg weight and shell quality. Where reported feed consumption is also reduced while effects on egg mass and feed efficiency vary according to light pattern.With asymmetrical or non-repeating light patterns there is an entrainment of ovipositions. Egg production is generally unaffected, and the exceptions to this are discussed. Where reported there is also no effect on feed efficiency and egg mass. Reports concerning the effects on egg weight vary.Bio-mittent lighting given during rearing results in a reduction of feed intake. With white egg strains point of lay body weight remains unchanged while with medium weight pullets body weight is restricted. Applied post-peak to white egg strains bio-mittent lighting gives an improvement in feed efficiency with no loss of egg production. There is also a small reduction in egg size together with increased shell thickness.The responses are discussed in relation to circadian theory and the photoinducible phase and it is concluded that further work is necessary.The economic benefits of the various lighting patterns are assessed and the relevance of the work to date to a wider commercial application is discussed.