Lambing date and its effect on the production and utilisation of grass-clover and lucerne pastures

Grass-clover and lucerne farmlets stocked at 15 and 20 ewes/ha respectively had similar yields of saleable products. From grass-clover the liveweight of lambs weaned was 583 kg/ha and the ewes produced 70 kg/ha of wool. On lucerne the liveweight of lambs weaned was 552 kg/ha and a wool clip from the ewes of 95 kg/ha. Lambing performance was relatively high from both pastures however on lucerne a significantly lower (P<0.05) lambing percentage (114%) was recorded than on grass-clover (166%). This was attributed partly to high coumestan levels in lucerne at the time of mating and partly to the occurrence of "border disease" in only the lucerne farmlets. Net pasture production recorded over the 12 month period was higher for both pastures than what was considered normal for the environment, 13 040 kg DM/ha from grass-clover and 20 120 kg DM/ha from lucerne. This was due mainly to the above normal rainfall over the trial period but in addition, net production from rotationally grazed pastures had not been previously recorded in this environment. Although annual DM production from lucerne was 54% higher than grass-clover total animal production was similar. This was due to; the greater seasonal variability of lucerne growth compared with grass-clover making it more difficult on lucerne to meet ewe requirements, especially over autumn winter and early spring. The in vitro digestibility of the total herbage present before grazing over the year was significantly higher (p