Procedure 5

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Determine rest period required to maximise regrowth between grazing events

Guidelines to determine rest period

Rest from grazing enables pastures to regrow and store energy reserves before the next grazing event. The main predictors of regrowth rate are temperature (maximum and minimum) and rainfall.  As a rule, when pasture growth is slow (winter and dry periods), the rest period needs to be longer; when pasture growth is fast (spring), the rest period can be shorter, but generally not less than 20 days.

Rest pastures after grazing for regrowth and to rebuild energy reserves

Post-grazing pasture phase (see Procedure 1) and groundcover are the major drivers for predicting the rest (regrowth) period required before the pasture is ready to graze again. Plan the grazing sequence of paddocks so that each paddock will be at the desired pasture quantity (kg green DM/ha) and quality (MJ ME/kg DM) at the start of grazing. See Tool 3.6 for plant-based grazing management methods.

Use pasture growth phenology to predict the date of regrazing each paddock

  • When the planned start date is too early (ie insufficient regrowth), slow the rotation by adding extra paddocks to the planned sequence, provide supplementary feed or consider the use of either a nitrogen-based fertiliser or gibberellic acid to promote growth of suitable perennial grass-based pastures.
  • When the predicted start date is too late (ie excessive growth), speed up the rotation by removing paddocks from the planned sequence.
  • Allocate any removed grazing units to other stock based on their grazing needs, or plan for fodder conservation, reseeding or later use as dry standing feed.

Determine the pasture rest (regrowth) period for your farm

Use a minimum pasture base of 1,000kg DM/ha and the formula:

(Number of days in the month) × (daily pasture growth rate*) = total monthly pasture growth (kg green DM/ha) for ungrazed pasture

* Tool 3.3 provides estimates of daily pasture growth rates across southern Australia that can be used to determine the rest (regrowth) period for your region.

The number of days’ rest can be estimated for any month by calculating each monthly pasture growth and adding these monthly totals to achieve a target of say, 2,500kg green DM/ha, at the start of grazing.

For further information on grazing management of grass and clover-based pastures, go to www.mla.com.au for Tips & Tools factsheets on pastures, weeds and grazing management (see Tool 3.4 for a list of relevant titles).

What to measure and when

When checking each grazed paddock, post-grazing pasture quantity and groundcover are the main indicators for predicting the rest (regrowth) period. Based on your measurements and observations, aim to predict the start of grazing to within +/- two days of the actual start date (see Tool 3.6 for methods).

The predicted rest period and planned start for the next grazing event can be delayed or advanced according to the:

  • monthly rate of pasture growth (see Tool 3.3)
  • growing season (good, average or poor, see Tool 3.3)
  • species composition of the pasture (see Tool 2.7)
  • measurement of post-grazing herbage mass (see Tool 3.1)
  • resource management requirements to maintain a productive pasture base.

Observations begin after removal of stock. When the planned or predicted start of the next grazing event is about seven days away, check more frequently to ensure grazing begins just before pasture energy content and growth starts to decline.

Commonly used grazing terms

Digestibility – a measure of the proportion of pasture or feed that, once consumed, can be used by the animal. Higher digestibility usually means higher animal production.

Dry matter (DM) – plant material without water. Usually expressed as a percentage of total weight of feed.

Fat score – an objective score of the extent of fat cover in live animals.

Feed intake – amount of feed eaten by an animal, measured in kilograms of dry matter per head per day (kg DM/head/day).

Feed on offer (FOO) – the total amount of above-ground, attached plant material, measured in kilograms of total dry matter per hectare (kg DM/ha).

Grazing unit – a set of paddocks that forms a distinct grazing management unit for one or more herds. It may be a rotation where a planned movement of the herd/s ends at the starting point, or an open-ended planned sequence within a planning timeframe.

kg DM/ha – kilograms of total dry matter of pasture per hectare, a measure of feed on offer (FOO).

kg green DM/ha – kilograms of dry matter of green pasture per hectare.

M/D – metabolisable energy content in feed dry matter, measured in MJ ME/kg DM.

Metabolisable energy – energy from feed that can be used for animal production.

MJ ME/kg DM – megajoules of metabolisable energy per kilogram of dry matter, a measure of the energy content of feed, directly related to feed digestibility.

Pasture availability – feed on offer (FOO), measured in kilograms of total green pasture per hectare (kg green DM/ha).

Pasture allowance (PA) – estimated maximum food intake plus an allowance for trampling and fouling, measured in kg DM/head/day. Also the pasture available divided by the number of stock.

Pasture growth rate (PGR) – daily growth measured in kilograms of dry matter of green pasture per hectare (kg green DM/ha/day).

Pasture quality – a measure of the energy content of feed, directly related to feed digestibility, measured in megajoules of metabolisable energy per kilogram of dry matter (MJ ME/kg DM). It can be calculated as 0.15 × dry matter digestibility %, or 0.16 × organic matter digestibility %.

Plant phenology – the growth stage a plant has reached in its maturation process. This term can be non-specific regarding observable measurements such as plants in growth phase I, II and III, or specific and measurable by terms such as number of live leaves per grass tiller, or the nature of lower clover leaves (alive or dead).

Plant senescence – the point at which ageing of a plant results in growth stopping in the plant or part of the plant. At this stage, energy accumulation ceases and net utilisable energy starts to drop in the plant or plant part.

Stocking density – the number of stock per hectare on a grazing area or unit at any one time, measured in head per hectare (head/ha); usually used to describe the number of stock per unit area in a high-density grazing situation.

Stocking rate – the number of stock on a paddock or a whole farm, measured in dry sheep equivalents per hectare (DSE/ha); usually used to describe the long-term stocking rate, at least on an annual basis.

Tactical grazing – the practice of using a range of grazing methods, through a single year or series of years, to meet different animal and pasture objectives at different times. Now recognised as the best grazing method.