In the agricultural area of Western Australia with its Mediterranean climate, most pastures are comprised of annual species, which actively grow from late autumn through to mid- to late-spring. However, irrespective of the rainfall and length of the growing season which can vary from less than 4 months in the eastern wheatbelt to more than 7 months in the high rainfall south-west there are periods in the year when pasture supply and livestock demand do not match.
The productivity of sheep is largely governed by the amount of pasture they eat, and this is influenced by the quantity and quality of the pasture on offer. Assessing pasture quantity and quality throughout the growing season gives managers the information they need to manage animal performance and pasture condition.
To estimate and manage FOO and to understand pasture quality and digestibility view the Factsheet.
Slow pasture growth in winter due to the cool temperatures can result in a shortage of feed, especially when there has been a late break to the season. Applying nitrogen fertiliser to pastures in winter can increase the growth of grasses and broadleaf weeds and help reduce feed shortages. On average, a producer can expect an extra 17 kilograms per hectare of pasture dry matter for every kilogram of nitrogen applied.
Dry annual pastures can provide good feed after senescence, however the quality declines rapidly to be less than a maintenance diet for stock. As a result, crop stubbles are generally the major feed source for sheep during the summer-autumn period. However, with increased harvesting efficiency and improved weed control, the grazing value of stubble paddocks has declined as they generally contain less grain and fewer weeds than in the past.
For example, while there is often up to 3 tonnes of available dry matter per hectare, sheep grazing stubbles may only eat about 6%.
Grazing annual pastures in the first 2-3 weeks after germination can dramatically lower the productivity of pastures during winter. Early grazing can reduce the plant density as seedlings are uprooted and reduces the leaf area available for photosythesis to sub-optimal levels.
The recommendation is to defer grazing of annual pastures at the break-of-season until feed on offer is at least 500–800 kilograms of dry matter per hectare (kg DM/ha). At this level, pasture plants are likely to be firmly rooted and have sufficient leaf area to be productively grazed.
Seasonal grazing based on feed on offer (FOO) can maximise stocking rate and pasture production.
Grazing management in winter and spring can manipulate the quality, quantity and composition of pasture. These changes in pasture composition can increase livestock feed efficiency and productivity, reduce insect populations and improve pasture persistence.
Feed measurements and feed budgeting is recommended to increase productivity and reduce livestock health risks.
To estimate FOO for an annual pasture paddock, check out this video:
Further information on grazing options and FOO targets are available in the grazing guide.
Grazing crops can help fill the autumn-winter feed gap and reduce the cost of supplementary feeding. However, careful grazing management is required to limit the potential negative impact on grain yield.
Why graze crops?
- Studies have shown that on mixed farms, utilising crops for grazing can potentially lead to a whole farm increase in gross margins.
- Both cereals and canola can be grazed by livestock and, with careful management, go on to produce acceptable yields.
- Pasture paddocks will benefit when livestock are removed as pasture can be left to grow and develop a ‘feed wedge’ to use for feed during winter when livestock are removed from the crops.
- Animal production may be higher as grazed crops may enable stock to increase intake (larger bite size) which could result in stock reaching their target markets earlier.
Considerations
- Early sowing is recommended to maximise biomass production for grazing.
- At the break of season, most crops germinate and grow faster than annual pastures. This biomass can be used for grazing livestock whilst the crop plants are still in their vegetative phase.
- Flowering times of crops can be delayed by grazing. This can be advantageous if it moves flowering past a frost window. However, if flowering is delayed too long this may push grain fill into a period of increasing temperatures and reduced soil moisture, which adversely affects grain yield.
- Seasonal conditions, such as a late break, can limit the potential of utilising crops for grazing.
- Some compromise may be required with the application of chemicals for the control of crop pests or weeds as withholding periods for stock need to be observed. Nitrogen applications should be applied after stock are removed.
Introducing livestock to crops
- Livestock should not be introduced to lush pastures or crops on an empty stomach. Feeding with hay is recommended prior to introduction and young stock vaccinated against pulpy kidney.
- A source of fibre should also be supplied and mineral supplementation including magnesium, calcium and salt may also be required.
- Livestock require an adaptation period to effectively utilise different sources of feed and gain maximum nutritional benefit. DPIRD research has shown that the grazing period may need to be longer than 4 weeks, particularly when grazing canola.
- Graze earlier rather than later but stock should be introduced to the crop only when the plants are securely anchored in the ground and there is enough biomass available for the desired stocking rate. Low stocking rates over a longer grazing period is easier for management but this can lead to uneven grazing. Any withholding periods on seed treatments should also be observed.
Removing livestock from crops
- To reduce the impact of grazing on crop yield, stock should be removed by the beginning of stem elongation (growth stage Z30) in cereals or the beginning of bud formation in canola.
- Post-grazing biomass, subsequent rainfall and growing season length can all affect crop recovery. Grazing crops lightly (‘clip’ grazing the top of the plant) and early in the growing season results in far smaller yield reductions than heavier and later grazing.
Further information is available to download:
The department has designed a range of tools, calculators and resources to help producers manage their ewe flock more effectively and make better management decisions about feed budgeting and grazing.
Agricultural and pastoral rangelands reports
Reports on sustainable natural resource use in agriculture and pastoral rangelands in Western Australia.
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