The variations in eating and rumination behaviour occurred among sheep under a constant feeding condition were investigated. Eleven Japanese Corriedale sheep (5 male sheep, 2 wethers and 4 female sheep), ranging in weight 22-39 kg and in age 1-9 yr. old, were used. Each sheep was given a timothy hay diet of 1.8% of body weight per day. During the 5 day period, record of jaw movement of each animal was measured daily, by using a pen-writing recorder joined with strain gauge amplifier and wire strain gauge held under the jaw of sheep.
Among individual animals great variations in eating and rumination time during 24 hr. were found. Range of values for individnal sheep were 71-177 min. for eating and 378-719 min. for rumination, and larger animals have a tendency to show longer rumintion time. Number of boli regurgitated daily and rumination periods were also variable for animals, ranging 356-617 and 14-44, respectively. The regions for some values measured on each bolus were 59-81 sec. for cyclic rate of regurgitation, 44-67 sec. for bolus time and 45-71 for chews per bolus. Chews per minute of cud also varied for individual animals from 58 to 98.
It was difficult to find a certain relation between eating or ruminating behaviour and apparent digestibility of experiment diet measured for each animal.