P.PSH.1245 Final Report

Summary

The composition and nutritional characteristics of WA diverse and variable northern rangeland pastures are not well known, which in turn is a major driver of beef cattle productivity in WA rangelands. This project aimed to identify where and what cattle in WA rangelands graze and how this impacts their productivity. Grazing locations and spatial assessment of the cattle movement were estimated by georeferencing cattle using GPS-enabled devices. The grazing ‘signatures’ were obtained from plant DNA detected in animal faeces by DNA metabarcoding, and this information was then integrated with vegetation and plant nutritional profiles, to understand what makes up the grazing palate for beef cattle in WA rangelands. All of these inputs (grazing location, plant data and presence in faeces) were then linked to animal productivity parameters (i.e. liveweight and liveweight gain) towards developing better grazing management practices that improve production, deliver a more consistent supply of animals, and improve rangeland health.

The project was impacted by the Covid-19 pandemic, restrictions on regional travel in WA, cyclone, flooding, pastoral access, and staffing issues. However, significant progress was made. In this project, a comprehensive approach was taken – from establishing a list of key plants species to be nutritionally mapped, cattle location, grazing patterns, diet selection to an overall effect on animal productivity has been have developed, applied and validated. A body of knowledge was generated of where and what beef cattle graze, and how it may affect the productivity data in the WA rangelands.

It was found that there is a great spectrum of nutritive plant profiles (nutritive values, NV) in WA rangelands. It was also confirmed that faecal plant DNA (fDNA) metabarcoding can be used to obtain more precise information on what animals are actually grazing. It was detected where animals are grazing, and then from the land vegetation profiles and fDNA profiles, grazing plants and grazing palates identified. It was also revealed which attributes (vegetation profiles, NV, diet selection) may potentially improve animal production. This project provided an approach and methodology that can be now applied across different regions, landscapes, plant mosaics, as well as over longer period of time. There was also engagement with the key grower groups and producers in the region.

Objectives

The overall objective of this project was to obtain quantitative data on NV, diet selection and the grazing patterns of the cattle in WA rangelands and to assess the link between diet selection and cattle growth rates.
Specific objectives were:
1. Quantify the diversity and variability of pasture species in the WA rangeland feedbase that supports beef production (literature search and database).
2. Examine animal grazing locations (via animal GPS positioning).
3. Examine NV of plant species that make up northern WA rangelands (via wet chemistry and NIRs spectral analysis).
4. Evaluate diet preference/grazing plant selection (via fDNA metabarcoding).
5. Investigate animal performance (LW/LWG from physical or WOW weighing).
6. Correlate animal diet selection with animal productivity.

Key findings

This project developed and validated a novel approach for feedbase mapping in the WA Rangelands. Firstly, the geo-referencing via Ceres tags and GPS collars is identified as a valuable tool to reveal where animals are grazing. In conjunction with other data such as land systems and profiles, revealed a preference for certain locations and vegetation profiles and allowed identification of preferred grazing areas. It was also identified that there is a wide choice of plants in the rangelands with favourable NV, which in turn can advance productivity of beef cattle.

The FDNA metabarcoding had proven to be good tool for more accurate identification of what cattle actually graze. Some preliminary data on diet selection are obtained and potential grazing palate in the central and northern WA Rangelands revealed. The fDNA analysis also enabled discovery of many additional species that have not been reported earlier using classical approaches. Using a local laboratory and database was proven to have the advantage over using a foreign laboratory and a global database, in the sense that it allowed more precise identification of plants that are present in Australia and the region. It appears that preliminary data on animal LWG can be linked to their grazing location and plants to identify what is driving the productivity.

Benefits to industry

Quantifying diet composition and selection of beef cattle in WA Rangelands can help in decision making by pastoralists to achieve desired objectives through predicting outcomes of grazing strategies and identifying key plant species to guide management. Such information is critical because individual cattle consume different quantities of nutrients and animal nutritional needs fluctuate. Diet composition of animals in extensive and spatially heterogeneous environments is difficult to identify because it is hard to locate animals, plant composition varies spatial and temporal and finding, identifying and analysing plants is difficult, complex, and time consuming.

The information that is collected will be used to form guidelines for grazing management decisions and improved production. A better understanding of these factors will guide management decisions and potentially improve production. The potential production benefits from improved management decisions include improved performance of individual animals, a reduced ‘tail’ in the spread of liveweights, higher reproduction rates, and greater predictability in achieving target live weights.

MLA action

Further research work into the potential of fecal metabarcoding as a land condition tool could be a gamechanger for industry.

Future research

This project, (and other outputs from the WA BEEFLINKS) will form the basis for developing grazing management practices that improve production, deliver a more consistent supply of animals, and improve rangeland health. One of the main outcomes from this project is the development of guidelines for improving grazing management to better utilise the mosaic of feed sources available to increase productivity and sustainability of beef production. These guidelines will be a blueprint for all northern WA beef producers to enhance the supply chain at its origin and, in combination with the BeefLinks – Growing WA backgrounding through adoption project, improve the efficiency down the entire supply chain from north-south. The fDNA metabarcoding is a unique method still in development, but as technology advances and its use becomes more widespread, the procedure will become standardized and accurate. Ideally, a pilot study for each new application should be conducted to ensure that the sampling and analysis design is appropriate to detect the target.

Database quality and imprecise taxonomic resolution are issues yet to be overcome. Future work should focus on i) improving the reference library with more sequences of plant species relevant for the whole WA rangelands; ii) understanding limitations of the method, i.e. that multiple species may be attributed to the same Zotu; iii) greater verification of fDNA metabarcoding results using field-derived plant composition data, especially in rangeland settings where plant diversity can be intrinsically high.

While the current project was guided to collect and analyse plants based on the pre-existing information and knowledge, the later geo-referencing detection of preferred grazing area and looking at fDNA revealed what cattle may have grazed. Once these are defined, it is be possible to go back to these areas and look specifically for plant species identified with the later approach.