The characterization of irrigated Midmar Italian ryegrass in the south eastern Transvaal Highveld using slaughter lambs.

Abstract

Reports the results of a study conducted to characterize the seasonal growth rate and changes in the quality of herbage, animal production and grazing capacity of Midmar Italian ryegrass in the South Eastern Transvaal Highveld under continuous grazing; Four levels of available dry matter (DM) were maintained on a continuously grazed irrigated Midmar Italian ryegrass (Lolium multiflorum Lam.) Pasture by means of a "put-and-take" grazing procedure. The pasture was stocked with three successive sets of weaned lambs in winter, spring and early summer respectively. The relation between average daily gains (ADG) and available DM was positively linear. At equivalent levels of available DM, gains were greater in spring than in either the winter and summer periods (P<0,01) but there were no differences in gains between winter and summer. There was a negative linear relation between average stocking rate (the rate required to achieve a given level of herbage availability) and available DM. Stocking rates in spring and summer were not significantly different, but both were higher (P<0,01) than those in winter. Within the range of the differential treatments applied, relations between stocking rate and ADG were negatively linear, and there was an interactive effect (P<0,01) between stocking rate and grazing period. Changes in ADG with a unit change in stocking rate were greatest in winter, intermediate in summer and least in spring. Gains/ha were curvilinearly related to available DM. The curves indicate that the amounts of available DM required for maximum gains/ha were least in spring, intermediate in summer and greatest in winter. From a serial cutting trial conducted concurrently with the grazing, a growth rate curve was developed for Midmar ryegrass. This curve had two maxima, with the maximum growth rate in spring being more than double that in autumn. The in vitro digestible organic matter content and crude protein content decreased.

Keywords: Animal production; average daily gain; Continuous grazing; crude protein content; Dry matter; ermelo district; Grazing capacity; growth rate; Herbage availability; italian ryegrass; Lolium multiflorum; Midmar Italian ryegrass; organic matter; Seasonal growth rates; Slaughter lambs; south africa; stocking rates; Transvaal Highveld

Journal of the Grassland Society of Southern Africa.