The nutritive value of some pasture species in north-western Australia during the late dry season

Abstract

The nutritive value of five pasture species, Mitchell grass (Astrebla elymoides F. Muell.), Flinders grass (Iseilema fragile S. T. Blake), native sorghum (Sorghum australiense Garber and Snyder), Birdwood grass (Cenchrtis setigerus Vahl), and buffel grass (Cenchrus ciliaris L.) harvested in the late dry season, were compared with a basic low quality roughage (rice straw, Oryza sp.) in digestibility trials with Peppin Merino sheep. Dry matter and organic matter digestibilities were Mitchell grass 45.2 and 48.2, Flinders grass 38.8 533 and 44.4, native sorghum 39.0 and 43.2, Birdwood grass 35.9 and 38.6, buffel grass 42.5 and 44.2, and rice straw 32.1 and 46.3. Voluntary dry matter intake, the concentration of ruminal ammonia and volatile fatty acids, and the digestible energy values were low with all species, and the possibility of primary energy deficiencies on dry season pastures is discussed. The efficiency of nitrogen utilization at low levels of nitrogen intake was higher than anticipated from published data, and further studies are in progress to verify these observations. The seasonal changes in chemical composition of the five pasture species studied are recorded in an appendix.