Seasonal diet selection by ewes grazing within contrasting grazing systems

Grazing management systems seek to control the relationship among animals, plants and soil by regulating the number of animals and the duration and location of animals. A greater understanding of the diet selection and activity of livestock within grazing systems will assist producers to make informed management decisions about their management within complex pastures. In the present paper, differences in the diet quality, selection and activity of ewes managed within contrasting systems (continuous-grazing (CG) and an intensive (20-paddock) rotational-grazing (RG) system) within a native pasture in the Central Tablelands of New South Wales, using non-invasive methodologies, are described. During two time periods (late spring and early autumn), the animals grazing within the CG system consumed a diet of higher quality and spent less time active than did those within the RG system. These differences resulted in higher individual animal production of CG animals that were able to maintain the herbage of preferred areas in a vegetative and highly nutritious state. The grazing animals selected the green herbage of higher quality than the average pasture and adjusted their selection seasonally. An underlying mechanism driving selection is the green:dead ratio of the herbage. Practically the results indicated that the green:dead ratio (or greenness) of herbage may provide a management trigger to enhance the production of animals grazing within a RG system, in particular during periods of higher requirement.