Effect of Short Day during a Growing Period on the Following Egg Production in Chicken

Abstract

There are plenty of reports on the effect of the lighting on chickens under condition of 24 hours of day length. A few reports on the effect of day length itself have been published, but they were examined with the effect of length in a laying period. There are few reports on the effect of day length in a growing period on chickens.Meanwhile, some data show that increasing of egg weight is closely related to days of age in chickens which are calculated based on 24 hours of day length. It is therefore reasonable to consider that shortening or lengthening of day length may affect increasing of egg weight in chickens.The purpose of these experiments is to determine whether 4 hour-shortening of day length has any effect on egg weight and production in Crossbred White Leghorn chickens which are reared from 0 or 8 to 28 weeks of age under the condition of 20 hours of day length.In experiment 1, four treatment groups were designed. Birds of group 1 were reared under the condition of lighting naturally, group 2 were under 20 hours of day length in the equal ratio of the length of the dark and light periods to that of lighting naturally, group 3 were under 16 hours of the light and 8 hours of the dark periods, and group 4 were under 20 hours of day length, 16 hours light and 4 hours dark. All birds were reared under the abovementioned conditions from 8 to 28 weeks of age.In experiment 2, two treatment groups were designed. Birds of group 1 were reared under the condions of 16 hours of the light and 8 hours of the dark periods and group 2 were 16 hours light and 4 hours dark.In experiment 3, four treatment groups were also designed. Birds of group 1 were reared under the condition of lighting naturally, group 2 were 16 hours light and 8 hours dark, and group 3 and 4 were 16 hours light and 4 hours dark. All birds in experiment 2 and 3 except group 4 of experiment 3 were reared under the abovementioned conditions from 0 to 28 weeks of age. Birds of group 4 of experiment 3 were reared under the condition of 20 hours of day length from 0 to 48 weeks of age.These experiments were terminated at 48 weeks of age.Age of sexual maturity was not changed in chickens reared under the condition of 20 hours of day length.Egg weight at sexual maturity was heavier in chickens reared under the condition of 20 hours of day length than that in chickens under 24 hours of day length except the group reared under 24 hours of day length and whose age of sexual maturity was extremely late.Egg weight in the begining of laying period of the chickens reared under the condition of 20 hours of day length was always heavier than that of the chickens under 24 hours of day length.Twenty hour day length had little effect on egg weight after 28 weeks of age and average of egg weight during the periods of experiments was a little heavier in groups of 20 hours of day length than in groups of 24 hours of day length.There was no difference between the groups of 24 hours and 20 hours of day length in egg production, feed comsumption, body weight and viability.