The utilization of spear grass (Heteropogon contortus). II. The influence of sulphur on energy intake and rumen and blood parameters in cattle and sheep

Abstract

Sheep and cattle were used to study the influence of nitrogen and sulphur on the consumption and digestion of spear grass. With sheep, additions of sulphur to the diet increased the digestibility and intake of the feed. The relatively high levels of plasma urea which were found in sheep fed on spear grass alone, decreased with sulphur intake. In cattle, sulphur supplementation did not increase the digestibility of feed. The levels of plasma urea were comparable with those of sheep receiving additional sulphur, which suggested that sufficient sulphur was returned to the bovine rumen to maintain digestion. As previously shown, feed intake was further raised in cattle receiving supplements of nitrogen and sulphur. With the addition of sulphur to the diet of spear grass and urea, the concentration of rumen ammonia was reduced and more nitrogen was retained. The levels of serum sulphate in groups of heifers fed in yards or at pasture demonstrated that sulphur may be limiting for the optimum utilization of spear grass in particular situations.