Effect of ewe stocking rate in spring on subterranean clover persistence and lamb liveweight gain

Abstract

Liveweight gain of ewes and lambs and subterranean clover reproduction were measured in tall fescuesubterranean clover pastures on a dry, stony soil stocked at 10 (low) and 20 (high) ewes and their twin lambs/ha over 46 days in spring 2005. Lambs grew at 374 g/day at the low stocking rate and 307 g/day at the high stocking rate, meaning final liveweight was 3.1 kg higher at the low stocking rate. However, lamb liveweight gain/ha/ day was greater at the high (12.3 kg/ha/day) than the low (7.5 kg/ha/day) stocking rate. Ewes gained 2.2 kg at the low stocking rate and lost 4.9 kg at the high stocking rate, with most liveweight loss occurring in the second half of the grazing period when moisture stress restricted subterranean clover growth. There were 62% fewer burrs/ m2 at the high than the low stocking rate. For both stocking rates, inadequate seed production resulted in inadequate seedling numbers in the following autumn (285 and 223 seedlings/m2 at low and high stocking rate, respectively). The results show high lamb liveweight gains can be obtained on subterranean clover pastures, but, in a drier than average spring, selective grazing of the clover may result in poor subterranean clover seed production and reduced seedling numbers in the following the autumn. Keywords: liveweight gain, seed production, sheep grazing, stocking rate, subterranean clover, tall fescue