The effect of intensity of rotational grazing with breeding ewes on phalaris-subterranean clover pastures

Abstract

Animal production and pasture amount and composition are presented from an experiment at Canberra in which one-, three-, and nine- subdivisions were rotationally grazed throughout the year in 1963, from December to September 1964, and from March to September in 1965, 1966, and 1967, at 20, 25, or 30 Merino ewes per hectare for three years, and at 17 ewes per hectare for a further two years. Intense subdivision resulted in pastures in which perennials, rather than the annual components, predominated. Moderate subdivision produced a pasture in which both perennials and annuals contributed substantially. Under a one-paddock (set stocked) system the annuals yielded more in spring than did perennials. Intensive subdivision favoured winter production, but resulted in less growth from pastures during spring, less dry feed in summer, and hence an increased need for supplementary feeding in years with dry autumns. The three-paddock system resulted in more winter production than the one-paddock, and about the same production in spring. Intensity of subdivision had little effect on animal production, except in increased frequency of deaths from Phalaris poisoning, some reduction in pre-lambing mortality, and increased requirement for supplementary feeding for survival. These results indicate that intensive subdivision of such pastures is unlikely to be worthwhile in environments such as that at Canberra. A moderate amount of subdivision as exemplified in a three paddock rotation, may give worthwhile increases in winter production, without the penalty of decreased spring growth.