Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 4. Animal production
W. H. Burrows A B , D. M. Orr A C , R. E. Hendricksen A B , M. T. Rutherford A , D. J. Myles A B , P. V. Back A B and R. Gowen AA Department of Employment, Economic Development and Innovation, PO Box 6014, Rockhampton Mail Centre, Qld 4702, Australia.
B Retired.
C Corresponding author. Email: david.orr@deedi.qld.gov.au
Animal Production Science 50(4) 284-292 https://doi.org/10.1071/AN09145
Submitted: 5 November 2009 Accepted: 12 April 2010 Published: 12 May 2010
Abstract
Steer liveweight gains were measured in an extensive grazing study conducted in a Heteropogon contortus (black speargrass) pasture in central Queensland between 1988 and 2001. Treatments included a range of stocking rates in native pastures, legume-oversown native pasture and animal diet supplement/spring‐burning pastures. Seasonal rainfall throughout this study was below the long-term mean. Mean annual pasture utilisation ranged from 13 to 61%. Annual liveweight gains per head in native pasture were highly variable among years and ranged from a low of 43 kg/steer at 2 ha/steer to a high of 182 kg/steer at 8 ha/steer. Annual liveweight gains were consistently highest at light stocking and decreased with increasing stocking rate. Annual liveweight gain per hectare increased linearly with stocking rate. These stocking rate trends were also evident in legume-oversown pastures although both the intercept and slope of the regressions for legume-oversown pastures were higher than that for native pasture. The highest annual liveweight gain for legume-oversown pasture was 221 kg/steer at 4 ha/steer. After 13 years, annual liveweight gain per unit area occurred at the heaviest stocking rate despite deleterious changes in the pasture. Across all years, the annual liveweight advantage for legume-oversown pastures was 37 kg/steer. Compared with native pasture, changes in annual liveweight gain with burning were variable. It was concluded that cattle productivity is sustainable when stocking rates are maintained at 4 ha/steer or lighter (equivalent to a utilisation rate around 30%). Although steer liveweight gain occurred at all stocking rates and economic returns were highest at heaviest stocking rates, stocking rates heavier than 4 ha/steer are unsustainable because of their long-term impact on pasture productivity.
Additional keywords: burning, economic evaluation, legume oversowing, steer age effects, steer liveweight gain, stocking rate.
Acknowledgements
Special acknowledgement is made to the Neill-Ballantine family (Galloway Plains Pastoral Co.) for their ready cooperation and for the long-term use of land on which the study was based. Many people contributed to the overall conduct of this grazing study during its 13 years duration and it is impossible to comprehensively list all these people here. We would especially acknowledge the large number of Department of Primary Industries and Fisheries and Department of Natural Resources and Water staff who provided major contributions to this study’s success. A Producer Advisory Group readily gave constructive advice throughout the study. Funding was provided by Meat and Livestock Australia.
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