Abstract
The experiment was performed in order to investigate the phase response of oviposition to a shorter light pulse and the precision of distinction of the length of the two dark periods under asymmetric skeleton photoperiods. 450 White Leghorn hens of 32 weeks of age were divided into two groups and treated the following asymmetric skeleton photoperiods; 9L:15D (light-on at 08:00), 9L:1D:1L:13D, 9L:4D:1L:10D, 9L:7D:1L:7D, 9L:10D:1L:4D, 9L:13D:1L:1D and 9L:15D. The order of the treatments in groups 1 and 2 was reversed. Each photoperiod was treated for three weeks and time of oviposition of each bird was recorded.
The phase response for the timing of oviposition to a 1 hour light pulse was 30 to 40 minutes under the photoperiods with two unequal dark periods, but the photoperiod of 9L:7D:1L:7D which is divided into equal dark periods the phase response was almost zero irrespective of the previous treatment. It is suggested that bird can distinguish the difference of the length of the two dark periods under asymmetric skeleton photoperiods very precisely.
