Selection by grazing sheep of pasture plants at low herbage availability and responses of the plants to grazing
1986
Broom, D.M. | Arnold, G.W. (Commonwealth Scientific and Industrial Research Organization, Wembley (Australia). Div. of Animal Production)
Merino sheep grazing annual pasture at the beginning of the growing season when the amount of herbage on offer was small, preferred to graze Wimmera ryegrass (Lolium rigidum) or subterranean clover rather than capeweed (Arctotheca calendula) and Erodium botrys was avoided completely. When capeweed plants were grasped they were sometimes pulled up by the roots and then dropped so that the number of capeweed plants in the pasture declined. Supplementation with oats reduced grass intake. As grass height declined in the pasture, the rates of biting, stepping and head swinging increased. Whilst capeweed plants continued to increase in height during grazing, as did ungrazed controls, ryegrass and clover plants decreased or remained short. Herbage dry matter increased in all species, owing especially to basal growth. The proportion of shoots and petioles which were erect increased in ungrazed plants, but the proportion which were prostrate was much greater in grazed plants.
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