Grazing annual pastures – using feed on offer (FOO) as a guide

Page last updated: Friday, 15 May 2020 - 8:53am

Grazing management in winter and spring in South West Western Australia (SW WA) can manipulate the quality, quantity and composition of pasture. These pasture changes can increase livestock feed efficiency and productivity, reduce insect populations and improve pasture persistence. Seasonal grazing based on feed on offer (FOO) is described here to maximise stocking rate and pasture production.

The Department of Primary Industries and Regional Development recommends using feed measurements and feed budgeting to increase productivity and reduce livestock health risks.

Estimating feed on offer (FOO)

Watch the video showing how to measure FOO in the paddock. By using a quadrat (shape with a measured area), you can get reliable and repeatable measures of FOO, and this calibration can then be used to visually estimate FOO across paddocks with similar pasture composition.

We suggest you use a square quadrat with an open space of about 32cm on a side (shown in the video). This gives an area of approximately 0.1 square metre, which makes the conversion from average grams (g) of pasture cut and dried from the quadrats, to kilograms (kg) per hectare (ha) quite easy: grams of dry matter (DM) from the quadrat multiplied by 100 equals kilograms of dry matter per hectare.

For example, an average of 18g DM/quadrat = 1800kg/ha

Winter grazing

We recommend deferring grazing at the break of season, until pasture reaches at least 800 kilograms of dry matter per hectare. See Deferred grazing and sheep at the break of season for detailed information.

Annual pastures in SW WA are in a vegetative phase during winter. In this phase, plants are established and  mature enough to withstand being grazed and defoliated by animals.

In the cool, wet winter conditions:

  • Over-grazing can result in insufficient leaf area for maximum pasture growth.
  • Small plants with poor root development may be susceptible to cold stress.

A minimum feed on offer (FOO) of 1000 kilograms of dry matter per hectare (kg DM/ha) is recommended going into winter. However, the optimum pasture growth of clover dominant annual pastures occurs at about 1400kg DM/ha.

The general rule: higher FOO = higher leaf area = faster pasture growth.

Grazing during the vegetative pasture phase in winter is important to:

  • encourage plant tillering in grasses and branching in clovers
  • assist in weed control
  • maintain palatability by promoting young shoot growth.

Grazing management through the vegetative phase should aim to meet animal production needs, while being sensitive to the productivity and sustainability of the pasture. Tactics to increase pasture utilisation and profitability include:

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Spring grazing

Annual pastures in SW WA move into a reproductive phase in spring, characterised by flowering and seed set. Pasture growth rates are often at their highest in spring, and many paddocks grow faster than the stock can eat, leaving excess pasture.

Spring grazing management should aim to:

  • Control problem grass seeds – heavy grazing of the grasses at seed head development will reduce possible seed contamination of wool and skins, and change pasture composition in the following year.
  • Avoid overgrazing clovers and other legumes during flowering and seed set – sub clover (Trifolium subterraneum) buries its seed, but overgrazing at flowering will prevent seed set.
  • Conserve enough feed for livestock needs over summer (when all annual pastures are dry). Feed can be saved as dry standing pasture, hay or silage.
  • Dealing with this excess pasture is key in managing issues such as grass seed contamination, feed conservation for summer and effective seed set for the following year.

Grazing management during spring can influence pasture composition in both the current year and following season. It is also the time of the year where preparations should be made to manage the potential summer feed gap and summer grazing issues.

Top tips

  • Manage pasture pests such as red legged earthmite.
  • Consider pasture topping to control grass seed set.
  • Manage pastures for maximising clover seed set.

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FOO targets for sheep

FOO targets for animal production are not necessarily the same as for pasture production, so it is important to have clear aims for both pasture and animals. Pregnant Merino ewes in late pregnancy can maintain condition if winter FOO is more than 800kg DM/ha. However, lactating ewes at lambing will need FOO of around 1500–2000kg DM/ha to provide adequate daily feed intake.

FOO targets for pastures

In Table 1, lower and upper boundary FOO values are suggested for optimal growth of annual plants in the winter vegetative and spring reproductive phases.

Table 1 Suggested FOO boundaries for optimum growth of annual pastures in kg DM/ha. Note: *maximum seed production may require spring FOO as high as 5000kg DM/ha
FOO

Vegetative (winter)

Reproductive (spring)

Lower FOO

1000

1500

Upper FOO

2500

3500*

These boundaries are based on:

  • maintaining adequate leaf area during winter to maximise pasture growth rate.
  • managing spring pastures to ensure adequate seed is produced for the following year's pastures.

An efficient grazing system maintains FOO between 800 and 1400kg DM/ha in autumn/winter, and between 1400 and 2500kg DM/ha in spring. Within these ranges, pastures can meet animal intake requirements, and pasture growth and recovery from grazing will be maximised.

Photographs of FOO levels for different areas and different pastures

See the Australian Wool Innovation site for Feed On Offer (FOO) library online. The library includes photographs of many Western Australian pastures.

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Strip grazing

Strip grazing (or 'ration' grazing) in winter confines sheep into small areas or 'strips' in the paddock for short periods. Movable electric fencing is usually used to provide the strip boundaries.

By confining animals in a small area and monitoring FOO:

  • grazing pressure is more even across the confined area – the target FOO is the lower FOO in Table 1 (less selective grazing and camp sites), or the lower FOO level for the livestock requirements
  • the ungrazed pasture can grow to the upper FOO in Table 1 (with higher leaf area and faster pasture growth in these ungrazed areas)
  • overall pasture growth and feed utilisation is improved, which can allow potentially higher stocking rates and reduce the need for supplementary feed
  • livestock condition and wool growth and quality can be more easily regulated.

When would I use strip grazing?

  • To complement deferred grazing at the break of the season – to prevent FOO dropping below the lower boundary (Table 1)
  • Whenever grazing pressure is high – that is, when the rate of removal of pasture exceeds the supply of pasture. This occurs when pasture growth is slow and/or stocking rates are high.
  • Where grazing pressure is uneven in a paddock – grazing pressure tends to be more even with strip grazing.
  • Where pasture growth rates are low or plant density is low – strip grazing gives much more control of FOO levels to stay within FOO boundaries (Table 1).

How do I strip graze?

  • Defer the area to be strip grazed until FOO reaches at least 800kg DM/ha. Refer to the deferred grazing calculator.
  • Assess the starting FOO and use the formula in the strip grazing calculator to determine the residual FOO and the strip area required. Early in the season when pasture growth is slow, the strip area will be bigger.
  • Continue strip grazing until spring pasture growth rates can maintain FOO under higher stocking rates.
  • Dry sheep are generally used in strip grazing. Pregnant ewes may be strip grazed, although it is strongly advisable to monitor ewes during pregnancy to prevent condition score falling below 2.0. Strip grazing is not recommended during lambing.
  • Electric fencing is the most effective method of constructing the strips. There are several commercial options available.

The strip grazing calculator allows you to determine the area of the strip required for your sheep.

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Intensive grazing

Intensive grazing to a target FOO is a management technique that adjusts the amount of pasture eaten to match the growth rate of the pasture. That is, pasture consumption equals pasture production. This results in FOO remaining constant.

The major benefit of intensive grazing is that more pasture is utilised, rather than being left in a large surplus at the end of spring to decay in the paddock over summer and autumn.

Intensive grazing can be used to control daily feed intake and meet specific animal production targets. Feed intake by sheep is maximised when FOO reaches 1000–1500kg DM/ha in autumn/winter, or 2500–3000kg DM/ha in spring. There is no benefit in having more than this amount of FOO in front of a grazing sheep.

In practice, sheep can be concentrated into a smaller area of the farm as pasture growth rates increase through the season. Ungrazed paddocks can be used for silage, hay, forage crops or set up to maximise seed set for the following year. Intensive grazing can also affect other important characteristics of a pasture such as composition and insect populations.

When would I intensively graze?

  • Whenever pastures are growing rapidly
  • Usually in spring, but also in early breaks and mild winters with good rainfall
  • Not in a late break or dry season with low FOO (groundcover over the following summer and autumn may be inadequate to prevent wind erosion).

What are the benefits of intensive grazing?

The benefits depend on your particular objectives. Some of them are:

  • better utilisation of feed
  • controlling and improving pasture composition
  • controlling insect pests such as red legged earthmite
  • setting up paddocks for stock with higher intake requirements for example lambing ewes
  • setting up paddocks for fodder conservation, particularly silage
  • part of whole farm feed budgeting to allow long term carrying capacity to reach potential.

Contact information

Danny Roberts
+61 (0)8 9892 8535