Managing for rainfall variability: effect of grazing strategy on cattle production in a dry tropical savanna
Peter O’Reagain A C , John Bushell A , Chris Holloway A and Angela Reid BA Queensland Department of Primary Industries and Fisheries, PO Box 976, Charters Towers, Qld 4820, Australia.
B Queensland Department of Primary Industries and Fisheries, PO Box 1085, Townsville, Qld 4810, Australia.
C Corresponding author. Email: peter.oreagain@dpi.qld.gov.au
Animal Production Science 49(2) 85-99 https://doi.org/10.1071/EA07187
Submitted: 27 June 2007 Accepted: 27 August 2008 Published: 2 February 2009
Abstract
Rainfall variability is a challenge to sustainable and profitable cattle production in northern Australia. Strategies recommended to manage for rainfall variability, like light or variable stocking, are not widely adopted. This is due partly to the perception that sustainability and profitability are incompatible.
A large, long-term grazing trial was initiated in 1997 in north Queensland, Australia, to test the effect of different grazing strategies on cattle production. These strategies are: (i) constant light stocking (LSR) at long-term carrying capacity (LTCC); (ii) constant heavy stocking (HSR) at twice LTCC; (iii) rotational wet-season spelling (R/Spell) at 1.5 LTCC; (iv) variable stocking (VAR), with stocking rates adjusted in May based on available pasture; and (v) a Southern Oscillation Index (SOI) variable strategy, with stocking rates adjusted in November, based on available pasture and SOI seasonal forecasts.
Animal performance varied markedly over the 10 years for which data is presented, due to pronounced differences in rainfall and pasture availability. Nonetheless, lighter stocking at or about LTCC consistently gave the best individual liveweight gain (LWG), condition score and skeletal growth; mean LWG per annum was thus highest in the LSR (113 kg), intermediate in the R/Spell (104 kg) and lowest in the HSR (86 kg). Mean LWG was 106 kg in the VAR and 103 kg in the SOI but, in all years, the relative performance of these strategies was dependent upon the stocking rate applied. After 2 years on the trial, steers from lightly stocked strategies were 60–100 kg heavier and received appreciable carcass price premiums at the meatworks compared to those under heavy stocking.
In contrast, LWG per unit area was greatest at stocking rates of about twice LTCC; mean LWG/ha was thus greatest in the HSR (21 kg/ha), but this strategy required drought feeding in four of the 10 years and was unsustainable. Although LWG/ha was lower in the LSR (mean 14 kg/ha), or in strategies that reduced stocking rates in dry years like the VAR (mean 18 kg/ha) and SOI (mean 17 kg/ha), these strategies did not require drought feeding and appeared sustainable. The R/Spell strategy (mean 104 kg/ha) was compromised by an ill-timed fire, but also performed satisfactorily.
The present results provide important evidence challenging the assumption that sustainable management in a variable environment is unprofitable. Further research is required to fully quantify the long-term effects of these strategies on land condition and profitability and to extrapolate the results to breeder performance at the property level.
Additional keywords: stocking rate, Southern Oscillation Index, pasture spelling.
Acknowledgements
We are grateful to the Lyons family of ‘Wambiana’ and the Wambiana Grazier Advisory Committee for their continued interest, guidance and support in running the trial. Peter Smith, Bob Shepherd, Geoff Fordyce, Alan Laing, Andrew Ash, Joe Rolfe, Ken Day and Greg McKeon as well as other DPI&F and CSRIO colleagues provided valuable advice in the planning and execution of many aspects of the trial. Richard Allen, Colin Bredden, Peter Fry, Dave Smith and Peter Allen assisted with the collection of field data. Animal condition was scored by John Bushell, Dave Smith and Geoff Fordyce. Trial establishment was funded via the Australian Government’s Drought Regional Initiative. Funding support for the project has been provided by Meat and Livestock Australia, the Natural Heritage Trust, the Great Barrier Reef Marine Park Authority and the CRC for Tropical Savanna Management. Previous comments by Mick Quirk, Rodd Dyer, John McIvor, Geoff Fordyce and Neil McDonald and two anonymous referees on the paper are gratefully acknowledged.
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