The utilization of spear grass (Heteropogon contortus). III. The influence of the level of dietary sulphur on the utilization of spear grass by sheep

Abstract

The effect of additions of sulphate to a spear grass diet fed to sheep with or without urea supplements was studied. With spear grass (0.39 g nitrogen/100 g dry matter), sulphate additions did not improve intake or digestion, but nitrogen retention was improved. With urea-supplemented spear grass, sulphate additions caused an increase in intake, digestion, and nitrogen retention. Nitrogen retention reached a plateau of about 2.5 g nitrogen per day. Sulphate added in excess of that required for microbial synthesis was excreted mainly as urinary sulphate. Nitrogen and sulphur in blood, rumen liquor, urine, and faeces were determined and the interrelationships between these variables are discussed. The differences between results of this experiment and results previously reported are discussed in relation to the variation in nitrogen content of mature spear grass between years, and to nutrition of the grazing ruminant.