Foraging strategies on rangelands: Effects on intake and animal performance

Rangelands exhibit extreme spatial and temporal variability in forage quality and availability. The animals that utilise these rangelands have consequently evolved a range of foraging strategies in an attempt to cope with this variability and maintain nutrient intake. In general, animals respond to and exploit spatial variability at all scales by selecting those items or units which optimise the intake of digestible nutrients and hence animal production. Animals similarly employ a variety of strategies to cope with temporal variability on rangelands. These strategies may include adjusting foraging behaviour and/or exploiting critical resources or resource areas to buffer temporal variability in feed quality or supply. While current understanding of short term foraging processes operating in small scale, relatively simple environments is acceptable, our understanding and ability to predict longer term processes operating at the larger scale in more complex rangeland environments is poor. Consequently, our ability to predict foraging behaviour on rangelands and hence animal intake and production or the impact of animals on specific areas is severely limited. The major challenge therefor, is to advance our current information, theory and models upwards from the small scale to accommodate and realistically simulate, the larger, more complex systems operating on rangelands

Principles of sustainable grazing management for the northern savannas

An urgent need exists for the development of principles for the sustainable management of the savannas of northern Australia. Based on current and recent research we propose five principles for the sustainable grazing management of these systems. These are (i) conservative use of the grass layer with utilisation levels of 15-25 % of annual pasture growth (ii) even utilisation of pasture at the paddock scale to prevent localised overgrazing (iii) regular wet season spelling to maintain pasture vigour and condition (iv) prescribed fire to manage savanna structure and improve rangeland condition and (v) managing for biodiversity by protecting areas of high conservation value. We suggest that these principles can be applied using relatively simple systems of grazing management

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

Inter-annual rainfall variability is a major challenge to sustainable and productive grazing management on rangelands. In Australia, rainfall variability is particularly pronounced and failure to manage appropriately leads to major economic loss and environmental degradation. Recommended strategies to manage sustainably include stocking at long-term carrying capacity (LTCC) or varying stock numbers with forage availability. These strategies are conceptually simple but difficult to implement, given the scale and spatial heterogeneity of grazing properties and the uncertainty of the climate. This paper presents learnings and insights from northern Australia gained from research and modelling on managing for rainfall variability. A method to objectively estimate LTCC in large, heterogeneous paddocks is discussed, and guidelines and tools to tactically adjust stocking rates are presented. The possible use of seasonal climate forecasts (SCF) in management is also considered. Results from a 13-year grazing trial in Queensland show that constant stocking at LTCC was far more profitable and largely maintained land condition compared with heavy stocking (HSR). Variable stocking (VAR) with or without the use of SCF was marginally more profitable, but income variability was greater and land condition poorer than constant stocking at LTCC. Two commercial scale trials in the Northern Territory with breeder cows highlighted the practical difficulties of variable stocking and provided evidence that heavier pasture utilisation rates depress reproductive performance. Simulation modelling across a range of regions in northern Australia also showed a decline in resource condition and profitability under heavy stocking rates. Modelling further suggested that the relative value of variable v. constant stocking depends on stocking rate and land condition. Importantly, variable stocking may possibly allow slightly higher stocking rates without pasture degradation. Enterprise-level simulations run for breeder herds nevertheless show that poor economic performance can occur under constant stocking and even under variable stocking in some circumstances. Modelling and research results both suggest that a form of constrained flexible stocking should be applied to manage for climate variability. Active adaptive management and research will be required as future climate changes make managing for rainfall variability increasingly challenging

On-farm demonstrations of low-input methods for establishing legumes in central Queensland

In 2010 a three year Meat and Livestock Australia funded Producer Demonstration Site (PDS) was established to demonstrate low-input sowing strategies for achieving legume establishment in buffel grass (Pennisetum ciliare) pastures in central Queensland. Butterfly pea (Clitoria ternatea), burgundy bean (Macroptillium bracteatum) and siratro (Macroptillium atropurpureum cv. siratro and cv. Aztec atro) were sown by broadcast, direct drill and crocodile seeder methods. Intensive herd impact applied immediately post sowing was trialled to determine if seed germination and establishment would benefit from animal induced soil disturbance. Treatments with soil disturbance at sowing (direct drill and crocodile seeder) recorded higher first year legume numbers than broadcasting. Despite excellent rainfall in the first two years of the trial, strong population declines across all treatments were recorded in subsequent years, with similar plant populations per hectare recorded between treatments at the conclusion of the trial. The results from the application of herd impact were inconclusive. Siratro was the only species to persist within the buffel grass dominated pastures. This trial demonstrated that low-input sowing methods with little or no removal of grass competition achieved poor plant populations. Industry needs to adopt longer fallow management for moisture storage and control of grass when establishing legumes into existing grass pastures

Spatial and temporal effects of grazing management and rainfall on the vertebrate fauna of a tropical savanna

Grazing by domestic livestock is one of the most widespread uses of the rangelands of Australia. There is limited information on the effects of grazing by domestic livestock on the vertebrate fauna of Australia and the establishment of a long-term grazing experiment in north-eastern Queensland at Wambiana provided an opportunity to attempt an examination of the changes in vertebrate fauna as a consequence of the manipulation of stocking rates. The aim was to identify what the relative effects of vegetation type, stocking rate and other landscape-scale environmental factors were on the patterns recorded. Sixteen 1-ha sites were established within three replicated treatments (moderate, heavy and variable stocking rates). The sites were sampled in the wet and dry seasons in 1999-2000 (T-0) and again in 2003-04 (T-1). All paddocks of the treatments were burnt in 1999. Average annual rainfall declined markedly between the two sampling periods, which made interpretation of the data difficult. A total of 127 species of vertebrate fauna comprising five amphibian, 83 bird, 27 reptile and 12 mammal species were recorded. There was strong separation in faunal composition from T-0 to T-1 although changes in mean compositional dissimilarity between the grazing stocking rate treatments were less well defined. There was a relative change in abundance of 24 bird, four mammal and five reptile species from T-0 to T-1. The generalised linear modelling identified that, in the T-1 data, there was significant variation in the abundance of 16 species explained by the grazing and vegetation factors. This study demonstrated that vertebrate fauna assemblage did change and that these changes were attributable to the interplay between the stocking rates, the vegetation types on the sites surveyed, the burning of the experimental paddocks and the decrease in rainfall over the course of the two surveys. It is recommended that the experiment is sampled again but that the focus should be on a rapid survey of abundant taxa (i.e. birds and reptiles) to allow an increase in the frequency of sampling and replication of the data. This would help to articulate more clearly the trajectory of vertebrate change due to the relative effects of stocking rates compared with wider landscape environmental changes. Given the increasing focus on pastoral development in northern Australia, any opportunity to incorporate the collection of data on biodiversity into grazing manipulation experiments should be taken for the assessment of the effects of land management on faunal species

Wambiana Grazing Trial: Water Quality Update to Burdekin Dry Tropics NRM

Aside from the obvious issues of animal production, pasture condition and economic performance, a key issue in savanna management is that of soil loss and runoff. Increased sediment and nutrient inputs from grazing lands have been identified as major threats to the Great Barrier Reef (GBR) lagoon and water quality is obviously of major relevance to the grazing industry. However, an aspect usually given lesser prominence is that excessive loss of runoff and nutrients will inevitably compromise long term pasture and animal production. Previous studies conducted on grano-diorite and sedimentary landscapes in the Burdekin catchment showed that runoff and sediment loss increased sharply as cover declined (McIvor et al., 1995; Scanlan et al., 1996). However, neither study addressed the issue of nutrient loss from these systems. Furthermore, both studies were conducted on relatively small plots: under these conditions much of the sediment moved is likely to be redeposited before entering water ways, making it difficult to extrapolate sediment losses to larger catchment scales. Major knowledge gaps thus exist concerning the relationship between management and runoff in extensive grazing lands. These are firstly, how runoff and water quality are affected by grazing management on the relatively flat, infertile, tertiary sediments, which make up c. 20% of the Burdekin catchment. Secondly, how grazing management affects water quality. And thirdly, the extent (if any) of the trade-off between reduced soil loss and economic productivity in grazing management. To test the effects of grazing management on soil and nutrient loss, five 1 ha minicatchments were established in December 1997 under different grazing strategies on a sedimentary landscape near Charters Towers. The objectives of the trial are to: 1. Assess the relative ability of different grazing strategies to cope with rainfall variability in terms of their effects on animal production, economics and resource condition. 2. Develop new and practical sustainable management strategies based on seasonal climate forecasting to cope with present and future rainfall variability, and 3. Promote the adoption of these strategies through direct demonstration of the benefits of sustainable management

Scaling results up from a plot and paddock scale to a property - a case study from a long-term grazing experiment in northern Australia

Grazing experiments are usually used to quantify and demonstrate the biophysical impact of grazing strategies, with the Wambiana grazing experiment being one of the longest running such experiments in northern Australia. Previous economic analyses of this experiment suggest that there is a major advantage in stocking at a fixed, moderate stocking rate or in using decision rules allowing flexible stocking to match available feed supply. The present study developed and applied a modelling procedure to use data collected at the small plot, land type and paddock scales at the experimental site to simulate the property-level implications of a range of stocking rates for a breeding-finishing cattle enterprise. The greatest economic performance was achieved at a moderate stocking rate of 10.5 adult equivalents 100 ha(-1). For the same stocking rate over time, the fixed stocking strategy gave a greater economic performance than strategies that involved moderate changes to stocking rates each year in response to feed supply. Model outcomes were consistent with previous economic analyses using experimental data. Further modelling of the experimental data is warranted and similar analyses could be applied to other major grazing experiments to allow the scaling of results to greater scales