An experiment was conducted to study the eatiing and ruminating behaviors associated with eating grass diets of different physical properties. Three adult wether sheep of Japanese Corriedale, (about 52kg in weight) were used. In each of two experimental periods, sheep were given the same amount of dry matter(630g/day) either fresh grass or sun-cured hay made from the same herbage. In each experimental period, following a 5-day preliminary feeding, eating and ruminating behaviors were measured for five consecutive days.
The sheep ate fresh grass more slowly than hay, so it took 68% longer time of eating fresh grass than hay. The rumination activity in terms of time spent ruminating was about 25% longer in sheep given hay (334 min/day) than for sheep given fresh grass (268 min/day). However, when the rumination activity was measured by actual time in chewing cud or chewing numbers, increase of these activities in sheep given hay was not so greater as increase of ruminating time. The chewing time or chewing numbers in each bolus lessened when given hay as compared with fresh grass, while cyclic rate of regurgitation was relativly constant. It was seemed to suggest that difference of the rate of ruminal fermentation or the resistance to masticating action between two diets affected ruminating behavior in sheep.