Deferred grazing and sheep at the break of season in South West Western Australia

Page last updated: Wednesday, 5 May 2021 - 4:48pm

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Grazing annual pastures in autumn can potentially lead to a significant reduction in pasture seedling density, especially within the first 12 days after the break of season. Grazing in the first 12 days can lower the productivity of pastures during winter because there are fewer plants. The Department of Primary Industries and Regional Development recommends deferring grazing of pasture paddocks at the break-of-season until feed on offer is at least 500–800 kilograms of dry matter per hectare (kg DM/ha).

Deferred grazing improves annual and long-term production of annual pastures

Annual pastures are most productive when they have enough leaf area to capture solar energy and convert it to plant growth. Rather than measuring leaf area, we recommend using measures of feed on offer (FOO) to get the most out of pastures.

Manage grazing in the 3 distinct periods of pasture growth: establishment (autumn), vegetative growth (winter) and reproductive phase (spring):

  • in autumn – defer grazing until FOO reaches 500–800kg DM/ha
  • in winter – graze to maintain FOO above 1000kg DM/ha
  • in spring – graze to allow seed production of the desirable pasture species.

Establishment phase

Deferred grazing allows seedlings to develop a root and leaf system that can be grazed without reducing its persistence.

Grazing pasture soon after seedling emergence can dramatically reduce establishment because small seedlings get uprooted: this reduces plant density and leaf area, which results in reduced pasture growth for the rest of the season.

You can improve plant density and effective pasture establishment by decreasing grazing pressure, applying fertilizer (particularly nitrogen), or sowing pasture seed. An efficient grazing system should aim to maintain FOO between 800–1400kg DM/ha in autumn and winter.

Supplementary feeding or deferred grazing can help maximise pasture establishment.

Deferred grazing

Deferred grazing means excluding stock from pasture paddocks after the break of season to maximise germination and establishment of seedlings.

Deferred grazing has the greatest benefit when:

  • there have been false breaks and a reduced seed bank
  • stocking rates are high
  • there is a late break to the season and cold conditions.

After an early break of season (January, February or March) in warmer conditions, it is not usually necessary to defer grazing: it is better to graze this high quality feed to improve the condition of sheep and potentially reduce supplementary feed requirements. These pastures will have adequate time to reach desired production targets before winter.

What are the benefits of deferred grazing?

Deferred grazing helps establish a dense and productive annual pasture by preventing over-grazing during establishment. It is important to have established a productive pasture before mid-winter, as growth is naturally slowed at this time of the season. A minimum FOO of 1000kg DM/ha is desirable going into winter, but optimum pasture growth occurs at around 1400kg DM/ha.

The effects of deferment on plant density will be greater at higher stocking rates. Autumn deferment may be more appropriate for farmers at near-optimal stocking rates. In some seasons where pasture growth is very slow, deferred grazing may be most beneficial when combined with strip grazing because the accumulated pasture is rationed. Refer to the information on strip grazing on the grazing winter pastures page.

How do I defer graze?

Concentrate sheep on selected 'sacrificial' paddocks or laneways, leaving more productive paddocks ungrazed. Sacrificial paddocks should have low erosion risk. Paddocks entering a cropping phase may benefit from early grazing to remove weeds.

Feedlot or confinement feed sheep only if you have the resources to do so effectively. Be aware of the animal health risks associated with this practice.

The length of deferment should be governed by pasture growth. Defer to a minimum of 500kg DM/ha (Figure 1), or preferably 800kg DM/ha. Refer to the deferred grazing calculator for details.

Run older, dry sheep at higher stocking rates, allowing pregnant or lambing ewes access to deferred paddocks. Be aware that deferred grazing may lead to increased broad-leaf composition in the pasture.

Figure 1 A pasture of 500 FOO is the minimum FOO level for deferment

Food on offer and pasture growth rate assessments for the agriculture region

We providing a seasonally updated map of FOO and PGR during the growing season.

The general FOO and PGR information for a locality can be used in the supplementary feeding calculator for pregnant and lactating ewes and the deferred grazing calculator. However, we recommend that you get more accurate measures of FOO on your own property.

Contact information

Mandy Curnow
+61 (0)8 9892 8422
Danny Roberts
+61 (0)8 9892 8535