RUMEN ECOLOGY DRIVING PRODUCTIVITY AND LANDSCAPE ECOLOGY IN THE SHRUBLANDS OF THE WEST AUSTRALIAN RANGELANDS G.A. Brennan AE , J.T.B. Milton B , B.E. Norton C and G. Krebs D A Department of Agriculture and Food WA and the Centre for the Management of Arid Environments, PO Box 110, Geraldton, WA 6531 B School of Animal Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 C Centre for the Management of Arid Environments, Locked Bag 22, Kalgoorlie, WA 6433 D Department of Agribusiness, Curtin University of Technology, PMB 1, Northham, WA 6401 E Corresponding author. E-mail: gbrennan@agric.wa.gov.au ABSTRACT The halophytic shrubs of the West Australian (WA) semi-arid shrublands provide the microbes in the rumen of livestock with a relatively constant source of salt and rumen degradable nitrogen (RDN), but the supply of digestible organic matter (DOM) is often low. When the salt content of the drinking water is also high, the dietary preference of livestock is likely to be driven towards plant species with low salt content and adequate DOM. Perennial grasses are an important component of these species in shrublands as they can improve livestock productivity, especially in dry seasons. This dietary preference has important implications for livestock management when these species are in short supply. After decades of continuous and sometimes high grazing pressure, the perennial grasses of the WA shrublands are now restricted to protected niches under shrubs and fallen branches. The task of regenerating sustainable livestock production may require changes to grazing management that will regenerate and maintain perennial grasses. Kangaroos must also be controlled, as de-stocking alone has been found to lead to a six-fold increase in kangaroo numbers. INTRODUCTION Understanding the principles of ruminant nutrition is essential for designing sustainable production systems in shrublands. The WA shrublands have a highly variable climate. The annual rainfall is 200-250 mm with winter rain generating most of the forage. The region has many halophytic shrubs such as the Atriplex and Maireana species, and seasonally driven perennial and annual grasses and forbs (Watson 2003). The challenge to achieve good growth and lactation from livestock is to ensure good rumen function by providing the microbes in the rumen with an appropriate balance of RDN, DOM and other essential nutrients (Standing Committee of Agriculture 1990). The salts from the halophytic shrubs are likely to reduce the amount of food eaten (Masters et al. 2005). Thus it is important to provide adequate DOM of low salt content to dilute the salt and complement the high RDN in halophytes.