A comparison of the nutritional value of spear grass (Heteropogon contortus)-dominant pastures and Urochloa grass (Urochloa mosambicensis)

Abstract

Both spear grass and Urochloa grass were cut at six intervals between January and October, near Townsville, Queensland, and the herbages, which ranged in age from 37-296 days, were fed to sheep indoors to compare voluntary dry matter intake, dry matter digestibility, and intake and retention of nitrogen, sulphur, and phosphorus. The dry matter intake and intake of digestible dry matter of Urochloa were greater than those of spear grass but dry matter digestibilities were similar at the same stage of growth. After mid-March, voluntary intake of digestible dry matter of both pasture species by the sheep was less than the amount needed to meet energy requirements. Nitrogen and phosphorus concentrations were higher in Urochloa than in spear grass, but the reverse applied to sulphur. Sheep were in negative nitrogen, sulphur, and phosphorus balance after early March, even though both grasses had been fertilized with superphosphate.