Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 4. Animal production

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.

Sustainability of beef production from brigalow lands after cultivation and mining. 3. Pasture rundown, climate and grazing pressure effects

“…Variation in the amount and timing of rainfall caused large variations in liveweight gain between years, ranging from 74 kg/head in drought years to 192 kg/head (mean of 146) in the Control paddock, from 102 to 224 kg/head (mean of 169) in Rehab 2, and from 56 to 176 kg/head (mean of 130) for the shallow soil BMK 2 site with limited soil water holding capacity. Variability of liveweight gain caused by seasonal weather conditions is typical of pastures in the Brigalow Region (Bortolussi et al 2005a;Radford et al 2007;Burrows et al 2010) and was observed during the trial as large changes in liveweight gain during the year (from -0.26 to 1.62 kg/head. day; Melland et al 2021).…”

Sustainable grazing management for temporal and spatial variability in north Australian rangelands – a synthesis of the latest evidence and recommendations

“…Results from a 13-year stocking rate experiment using paddock sizes of 10 -40 ha in central Queensland showed that profitability was greatest at the heaviest stocking rate with an average pasture utilisation rate of about 61 % (Burrows et al 2010). Although rainfall over the trial period was generally well below average, no major pasture composition change occurred.…”

Sustainable management for rangelands in a variable climate: evidence and insights from northern Australia

“…However, all involved relatively small, uniform paddocks of between 3 and 30 ha, with small groups of animals (e.g. Burrows et al, 2010;Ash et al, 2011). This lack of scale and spatial complexity limits their relevance to larger, more heterogeneous commercial paddocks where production and rangeland responses may be significantly different (Ash and Stafford Smith, 1996).…”