The effects of continuous and rotational grazing of sourveld on the quality of herbage selected by Simmentaler heifers.

Abstract

A grazing trial was conducted at the Kokstad Agricultural station to compare the dry matter digestibility (DMD) and crude protein content (CP) of diets selected by four fistulated cattle which were continuously and rotationally grazing sourveld. Two stocking rates of 1, 0 and 2, 3 animals/ha (0, 5 and 1, 2 LSU/ha) were applied under each grazing method. The mean DMD and CP values of diets selected in the continuous and rotational grazing treatments, respectively, were: DMD = 64, 3%; CP = 6, 63%, 6, 88%. The effect of stocking rate on the quality of the diet selected varied between the two grazing methods. DMD and CP of diets selected under rotational grazing decreased with time during the week-long period of stay in each paddock. On average, DMD and CP values on the first and sixth day respectively, were: DMD=66, 6%, 60, 5%; CP=8, 37%, 6, 01%. These differences were more pronounced at the higher than at the lower stocking rate. It was concluded that, although some of the treatment differences were small, grazing method differences in the DMD of diets might at least partially account for observed differences in livemass gains under the two grazing systems.

Keywords: cattle; crude protein content; dry matter digestibility; grazing systems; grazing treatments; herbage; in vitro dry matter digestibility; kokstad; kokstad agricultural research station; live mass gain; oesophageal fistula; rotational grazing; south africa; stocking rate; stocking rates