Some variables influencing production of prime lamb and wool from pasture

Abstract

In an experiment at Canberra, A.C.T., extending over four years, crossbred and Merino ewes were grazed at three stocking rates on pastures of either phalaris (Phalaris tuberosa), phalaris combined with separate paddocks of brome grass (Bromus inermis), and cocksfoot (Dactyllis glomerata), or separate paddocks of brome grass and cocksfoot. Subterranean clover (Trifolium subterraneum) was present in all pastures. One-, two-, and three-paddock systems and two times of lambing were also compared. Pasture availability and animal productivity were measured. Early lambing resulted in more prime lambs although the later lambs had slightly higher rates of gain. At the highest crossbred stocking rate studied (seven ewes per acre) wool production per acre was still increasing, but number of prime lambs and lamb liveweight gain did not increase above stocking rates of five ewes per acre. More feed was available to ewes during late pregnancy on treatments allowing feed rationing in autumn and early winter, but neither rationing nor including brome grass and cocksfoot in the system increased animal productivity beyond that achieved by grazing phalaris continuously. At stocking rates up to six ewes per acre, animal production was greatest from phalaris grazed continuously. Stocking rates were designed to provide similar weights of either Merino or crossbred ewes per acre at each stocking level. Because more lambs were born to crossbred ewes they had less feed than Merinos in spring and summer at all stocking rates. Lambs from crossbred ewes were heavier at birth and grew faster than lambs from Merino ewes. More prime crossbred lambs were produced per acre at all stocking levels. The reproductive rate and lamb production of Merino ewes dropped sharply with increased stocking rate. Fleeceweights were similar for both breeds, particularly at low stocking rates. Wool production per acre increased with stocking rate and was higher from Merinos at each level.