Abstract

The risks for extensive cattle properties in the rangelands of northern Australia arising from high inter-annual rainfall variability are predominantly managed through adjustments in stocking rates (SR). This modeling study compared the performance of SR strategies that varied considerably in the extent that they adjusted SR annually at 3 locations in northern Australia. At all locations, land types and pasture condition states, the SR strategies that achieved the best pasture condition were those that least increased and most decreased SR annually in response to changes in forage availability. At Donors Hill (Qld), these conservative strategies also achieved the highest cattle liveweight gains per hectare (LWG/ha). While conservative strategies produced the highest percent perennial pasture species at Fitzroy Crossing (WA), strategies which allowed larger increases and decreases in SR also performed well, enabling them to also achieve high LWG/ha with little deterioration of pasture condition. A similar trend occurred at Alice Springs (NT), although at this location the strategies with even larger annual increases and decreases in SR achieved relatively high percent perennials and the highest LWG/ha. While systematic management of SR appears to perform better than a constant SR strategy when rainfall variability is high, it is unclear if the magnitude of annual adjustments in SR needs to increase with increasing rainfall variability.

Highlights

  • Annual forage growth in the north Australian rangelands is predominantly driven by rainfall (McKeon et al 1990)

  • The results of average percent perennials and average liveweight gains per hectare (LWG/ha) achieved by stocking rates (SR) strategies are shown for the high productivity land type in good pasture condition at each location

  • The highest values for percent perennials were achieved by strategies that limited annual increases in SR to 5% (Figures 1–3)

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Summary

Introduction

Annual forage growth in the north Australian rangelands is predominantly driven by rainfall (McKeon et al 1990). High annual variability in the supply of forage for livestock has significant implications for pasture condition and cattle productivity, where adjustments in stocking rate (head or adult equivalents per square kilometer) are the main means of managing these risks. Two broad approaches can be used to manage SR: fixed stocking (a constant SR); and flexible stocking (SR varying over time in response to changes in forage supply) (Buxton and Stafford-Smith 1996). The simulation study reported here compared fixed stocking with a number of flexible strategies, which vary greatly in the extent cattle SRs are adjusted annually in response to changes in forage availability

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