TEMPORAL VARIATION IN GRAZING BEHAVIOR OF SHEEP AND THE RELIABILITY OF SAMPLING PERIODS

Grazing behaviour recordings of 24 h duration are frequently taken to represent behaviour patterns typical of a longer period. This experiment tested the repeatability of patterns of grazing behaviour of nine Scottish Halfbred (Border Leicester X Cheviot) yearling female sheep (Ovis aries L.). Their behaviour was recorded continuously for 7 days between 25 February and 3 March 1992 using an automatic system which measured jaw movements. The mean times of sunrise and sunset during the experiment were 07:02 and 17:55 h. The animals were continuously stocked on a 0.65 ha perennial ryegrass paddock (Lolium perenne L. cultivar 'Parcour') where the sward surface height was maintained between 5 and 6 cm. The hour of the day had a significant effect on time spent eating, idling and ruminating in that hour. There was a recurrent daily pattern of grazing behaviour, which was modified by rainfall, There was also a within-day grazing pattern, with peaks in eating activity every 8 h. Prehension biting rate was significantly affected by hour of the day with a maximum rate of 79 prehension bites min(-1) between 03:00 and 04:00 h and a minimum in the late afternoon of 61 min(-1). Total jaw movements whilst eating reached a maximum of 167 min(-1) around the time of the late afternoon peak in eating activity. It was concluded that a 24 h recording could be taken as representative of grazing behaviour over a 7 day experimental period but care should be exercised to avoid bias due to atypical weather conditions.