Effect of the light and darkness cycle on eating and rumination behaviour in sheep fed on roughage diet alone.

In the present study, effect of the changes in daily light(L)and dark- ness(D)cycle on rumination behaviour in sheep fed roughage alone at a level of2.0or 2.2% dry matter per bodyweight per day in2times feeding a day or hourly feeding. The 4daily lighting treatments were as follows; Treatment I,12L+12D; Treatment II,6L+6D +6L+6D; Treatment III,24L, and Treatment IV,24 Di n trial1, and in trial2, Treatment I,12D+12L; Treatment II,6D+6L+6D+6L; Treatment III,24D and Treatment IV,24L. During the sampling period in each lighting treatment, the time spent chewing during eat- ing and ruminating was recorded. The eating behaviour was observed in each hour during lighting period in2times feeding a day. Daily eating pattern after hourly feeding was rela- tively steady in all the4lighting treatments. Daily total time spent ruminating tended to in- crease in Treatments I and II in2times feeding a day, and in hourly feeding the tendency was in opposition. There was no rumination at1hour after morning and evening feeding in2times feeding a day. In hourly feeding, on the contrary, there was no zero time spent ruminating per hour in all the lighting treatments. During continuous lighting, the rumi- nation pattern in the first half(09:00-21:00)and the latter half(21:00-09:00)was very similar after2times feeding a day, and that after hourly feeding was relatively steady for24hours. From these findings, it was confirmed in ruminant animals that the changes in daily lighting condition, in particular daily darkness pattern, could have clearly influenced