Pasture allocation

Over 12 months most paddocks will have 9 to 10 grazings. It only takes one poor grazing event to adversely impact the next 2 or 3 grazing events or the long-term production of that pasture.

Calculating pre-grazing cover

Calculating your pre-grazing cover will support you to achieve post-grazing residual targets, good animal performance and enable accurate pasture allocation.

Grazing residuals

Grazing residuals are the key indicator of pasture utilisation. Poor pasture utilisation results in high post-grazing residuals, i.e. pasture wastage.

High post-grazing residuals will suppress pasture growth rates and will reduce pasture digestibility at the next grazing, impacting animal performance.

In late spring, perennial ryegrass tillers move from vegetative to reproductive growth. This leads to stem elongation, and these reproductive stems contain high levels of fibre. This may lead to slight increases in post-grazing residual height if not managed well. If this continues then when feed becomes short, cows could be forced to eat lower quality pastures.

Achieving target residuals in spring will reduce the number of reproductive tillers, minimising the higher grazing residuals that could otherwise occur.

Consistent even-grazing height

For a ryegrass clover pasture, a consistent, even grazing height, few or no clumps, will be 7-8 clicks on the rising plate meter, 3.5cm to 4 cm compressed height or 1500 - 1600 kg DM per ha in spring.

The plate meter will overestimate residuals where there are weeds or there is pugging damage.

Calculating pasture growth rates

It is important to have pasture growth information for your farm for strategic planning such as, annual feed budgeting, identifying underperforming paddocks, and for tactical management such as, predicting a surplus situation.

Pasture growth is measured in kg DM/ha/day. Working out the growth rates for your farm requires good record keeping. In most cases, software available for feed wedges and pasture data can calculate growth rates at a farm level.

How to calculate growth rates

• Measure grazing residuals for each paddock (e.g. 1500kg DM/ha)
• Measure again before the next grazing (e.g., 2800 kg DM, therefore 1300 kg DM pasture grown since last grazing)
• Divide this by the number of days between measurements (e.g. 24 days)
• The average growth rate is 54 kg DM/ha/day

What you need: a board or spreadsheet to record each grazing date for each paddock and to record the corresponding pre-grazing cover and post-grazing residual.

This information can then be used as a guide for the next grazing round and following seasons. Saving this information will allow you to build up a file of data that can be used for feed budgeting purposes.

Effective grazing management

Managing grazing yield, pasture mass and leaf stage at grazing will enable correct decisions of the order paddocks are grazed, ensure the right pre-grazing and post-grazing targets are chosen, and that targets are achieved.

Understanding your target covers will support you to set the correct rotation length. Rotation length should be set based on the assessment of the leaf stage for your farm while ensuring the paddocks are grazed within the desired pre-grazing range.

Other things to consider for effective grazing management are:

• Accurate pasture allocation is driven by regular pasture assessment (e.g. weekly farm walks).
• Monitor cow intake and grazing residuals. This will tell you how accurate your pasture assessment is.
• Consider the management of leaf stage. Paddocks that have recently had nitrogen fertiliser applied may have higher yields at lower leaf stages as nitrogen increases leaf size.
• Consider your farm’s feed demand compared to the amount of pasture grown. This will be impacted by your stocking rate, as well as seasonal differences in pasture growth.
• Changes to pre-grazing yields and adverse weather events will make achieving residuals challenging. In prolonged periods of high rainfall, target residuals may not be attainable, however it makes good sense to correct these residuals when possible (e.g., removing the paddock from the grazing rotation to make silage, or topping the paddock post-grazing).