Grazing management of oversown tussock country 3. Effects on liveweight and wool growth of Merino wethers

Abstract

The liveweight performance, wool production, and wool characteristics of Merino wethers under nine different grazing management regimes for oversown tussock pasture on a steep (30°), south‐east facing hillside (760–930 m altitude, 500 mm annual rainfall) in New Zealand was measured for six consecutive years. Continuous stocking, alternating (two paddock), and rotational (six paddock) grazing were each compared at low, medium, and high stocking rates (1.9, 3.0, and 4.1 SU/ha/year, respectively). By the sixth year, alternating grazing at the medium stocking rate gave maximum liveweight gain/ha. An interaction was demonstrated, with advantage to alternating and rotational grazing over continuous stocking strengthening with increasing stocking rate. Liveweight gain for alternating and rotational grazing was similar at all stocking rates, showing an advantage in animal performance over that from continuous stocking can be achieved with a minimal amount of subdivision fencing. The advantage to alternating and rotational grazing over continuous stocking was most obvious during late spring/early summer, suggesting that in practical terms runholders need to consider such management for ewes in late lactation with lambs still at foot. Wool growth/ha increased linearly with increased stocking rate, with advantage to alternating and rotational grazing evident at high stocking rates. In contrast to the lowland experience with Romneys, the rate of Merino wool growth declined as the grazing season progressed. Fibre diameter was 1.5 μm less at the high than at the low stocking rate. Practical application is discussed, with emphasis on achieving a realistic balance between objectives to maximise wool production and those to sustain pasture production and maintain desired animal liveweight.