Comparison of sheep and cattle grazing on a semiarid grassland

Abstract

The botanical and chemical composition of the diet and changes in body weights of Hereford steers and Border Leicester x Merino wethers were compared over a 2-year period while grazing a semiarid grassland in adjacent paddocks. The grassland was a Danthonia caespitosa–Stipa variabilis type containing 200-800 kg per ha of green pasture consisting mainly of warm-season grasses, but also components of cool-season grasses, chenopod plants, medics and other forbs. The plots were permanently grazed by either sheep at 1.03 and 1.45 per ha or cattle at 0.13 and 0.18 per ha. Animals fitted with oesophageal fistulas were introduced at intervals to obtain estimates of the composition of the diet.

The intakes by the cattle contained less of the short medics and cool-season grasses and more dry herbage than those of the sheep. As a result the diets of the cattle were consistently lower in nitrogen than those of the sheep. However, the in vitro digestibilities of the diets of both the cattle and the sheep were similar.

The weight changes (expressed as either kg/ha or kg^0.9g/ha) of both species were in the same direction and of similar magnitude, and do not support the belief that the semiarid winter-rainfall areas are more suited to sheep than to cattle.