Response of lambs to continuous and rotational grazing at four grazing intensities on Midmar Italian Ryegrass.

Abstract

Reports the results of a study conducted to compare the effect of grazing procedure on the quantity and quality of the pasture as measured by the performance of weaned lambs grazing on Midmar Italian ryegrass; Irrigated Midmar Italian ryegrass (Lolium multiflorum Lam.) was grazed either continuously or rotationally at four grazing intensities by three successive sets of weaned lambs for the winter, spring and summer periods, respectively. The "put-and-take" system was applied. In the case of continuous grazing, amounts of available dry matter (DM) per hectare were varied, whereas with rotational grazing different grazing intensities were established by allocating different amounts of DM per unit livemass. Amounts of DM on offer were determined in both systems to provide a basis for comparison. There were no differences in average daily gain (ADG) at equivalent levels of available DM between grazing procedures in winter. In both spring and summer, however, ADG at given levels of available DM was greater (P<0.01) with continuous than with rotational grazing. Stocking rate at equivalent levels of available DM was higher (P<0.01) for rotational as compared with continuous grazing in winter and summer, but in summer, but in summer, grazing procedure had no effect on stocking rate. There was an interaction between stocking rate and grazing method in winter (P<0.01). At high stocking rates, ADG were higher (P<0.01) under rotational than under continuous grazing. In spring and summer the ADG for continuous grazing was higher (P<0.01) than that for rotational grazing at equivalent stocking rates. The estimated stocking rates for maximum gains/ha ranged in the different seasons from 45 to 123 lambs/ha.

Keywords: average daily gain; Average daily gains; Continuous grazing; dry matter; Dry matter availability; ermelo district; Grazing intensities; grazing intensity; Grazing management; grazing procedures; italian ryegrass; Lambs; Lolium multiflorum; method; Midmar Italian ryegrass; nooitgedacht research station; Pastures; Rotational grazing; south africa; stocking rate; Stocking rates

Journal of the Grassland Society of Southern Africa.