Studies on Pattern of Grazing Behavior of Lambs

Observations in the present paper were initiated at Experimental Farm of Hiroshima University, Fukuyama, in summer of 1959 and continued every year to October of 1961.The observations were carried out at monthly intervals from May to September or October to Iambs-4.5-10.O month old Corriedales-grazed on pasture of wild grassland a little under 4 ha wide. Observation technique taken was CHAMBER'S method (1959) in which activities of indi viduals under flock management were recorded at 4 min intervals throughout 24hr and they were classified as grazing, eating concentrates, eating hay, ruminating, resting and idling.From data obtained in 13 observations, it has been shown that there were three types in the pattern of grazing lamb's behavior. The first was a type of intensive grazing concentrated in daytime which was seen in flock grazed on spring pasture and the second was a type of grazing concentrated in nighttime seen in flock on midsummer pasture. The third was a breakup or dispersed type between daytime and night seen in flock on early summer or autumn pasture.The G R Ratio (grazing/ruminating ratio) from present data varied seasonally from about 2 in May through 1 in August down to 0.8 in September. Although leisurely grazing in spring (DORAN, 1943) must be considered, increase of grazing time in spring and decrease in summer were clearly pointed out. These seasonal variations in the pattern of lamb's grazing behavior would largely depend on variations of environmental temperature, daylength, grassland conditions and others. They were discussed with reference to regulation mechanism of body temperature.There were evidence of disturbed lamb activities in mixed grazing with cattle, but as these disturbance did not continue for long time, it would not appear therefore that grazing pattern of lambs was much influenced by cattle.