Stocking rate effects on liveweight gain of ewes and their twin lambs when grazing subterranean clover-perennial grass pastures

摘要

Two grazing experiments were conducted on non-irrigated tall fescue-subterranean clover and cocksfoot-subterranean pastures subject to summer-dry conditions in Canterbury, New Zealand, to measure the effect of low (83-10 ewes and their twin lambsha(-1)) vs. high (139-20 ewes and their twin lambsha(-1)) stocking rates (SR) on lamb and ewe liveweight gain in spring. In tall fescue-subterranean clover pasture, lambs grew faster at low (374g per headd(-1)) than high (307g per headd(-1)) SR, but total liveweight gain per ha was greater at high (123kgha(-1)d(-1)) than low (75kgha(-1)d(-1)) SR. In successive years in spring in cocksfoot-subterranean clover pastures, lambs grew faster at low (327, 385g per headd(-1)) than high (253, 285g per headd(-1)) SR but total liveweight gain per ha was greater at high (726, 791kgha(-1)) than low (543, 638kgha(-1)) SR. These studies indicate that in summer-dry areas, subterranean clover-based pastures will support high twin lamb growth rates in spring, with lower SR leading to higher lamb growth rates and more lambs reaching slaughter weights before the onset of dry conditions.