THE PATTERN OF DEFOLIATION OF COCKSFOOT BY GRAZING SHEEP

Abstract

The pattern of defoliation of cocksfoot by Romney sheep at two stocking rates (approximately 36 and 80 sheep/ha) was studied in the autumn. After an autumn "flush" of growth, pasture availability, pasture height and green leaf length showed a rapid then steady decline during the grazing period. The length of green leaf removed per defoliation was closely related to the length of leaf available - i.e.,-the shorter the length available, the shorter the length removed. The proportion of g&en leaf length removed, however, showed little change over the grating period. Tillers were, grazed every 5 or 6 days in the high-stocked treatment and every 7 or 8 days in the medium-stocked treatment. These were generally the taller tillers, particularly in the mediumstocked treatment. Evidence of preferential grazing of different aged tillers was not obvious. However, towards the end of ihe experimental period the youngest tillers in the, medium-stocked treatment were grazed less frequently but more severely than, older tillers. In the highstocked treatment the youngest tillers were less severely grazed than older tillers. Preference for the youngest leaves 0n.a tiller was evident in all treatments. The mean liveweight of sheep incre&ed on the medium-stocked treatment but decreased slightly on the high-stocked treatment. The plant and animal responses recorded are discussed.