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The effect of short light-dark cycles on egg production of laying hens were studied. Two hundred and forty female chicks of White Leghorn breed were divided into three groups immediately after hatch and reared in a windowless house. One group of chicks was exposed to 21-hour cycles composed of 15 3/4-hour light and 5 1/4-hour dark (15 3/4L: 5 1/4D, Treatment 21-21). The second group was exposed to the same 21-hour cycles, but the length of the cycle was changed into 24 hours (15 3/4L: 8 1/4D) at 20 weeks of age (Treatment 21-24). The remaining one group was reared under 24-hour cycle throughout experiment (Treatment 24-24). Motality, body weight gains and feed conversion ratio during the rearing period and the mean age at 50% lay were not significantly different among the three groups. Lengthening the light-dark cycle from 21-hour to 24-hour (Treatment 21-24) caused an increase in the egg production in the first stage (from 20 weeks to 32 weeks of age) of the laying period. In the same period, the feed conversion ratio and the clutch length in Treatment 21-21 were inferior to the other Treat ments (21-24 and 24-24).
日本家禽学会の論文