Grazing management options

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Successful pasture utilisation requires precise control of the grazing pressure and herd structure of the beef business. This tool provides the basis to determine how pasture can be successfully turned into saleable beef to profit the farm business.

By using the formulas provided, following the examples and then inserting your own working examples, you will be able to:

  • Estimate stocking rate over short periods;
  • Make tactical grazing decisions about the short-term stocking rate/ha;
  • Plan seasonal pasture and animal performance to achieve targets; and
  • Calculate the gross financial benefit to the grazing business.

This information enables the grazing operation to be more precisely managed. The conversion of pasture energy and nutrients into saleable beef is achieved while leaving pasture residue in the best condition for rapid regrowth. It will also better match the seasonal feed supply with beef enterprise opportunities and business objectives.

PROGRAZE information

To make the best grazing management decisions, some basic PROGRAZE or equivalent information is required:

  • amount of pasture (kg DM/ha) in a paddock, grazing block or whole farm
  • pasture quality (MJ ME/kg DM)
  • pasture growth rate (kg DM/ha/day)
  • stock to be grazed and the target weight gain required (kg/head).

The following estimates are used in the practical working examples:

Pasture at the start of grazing       2,500kg DM/ha

Pasture at the end of grazing        1,500kg DM/ha

Pasture quality                                10MJ ME/kg DM

Pasture growth rate                         30kg DM/ha/day

Pasture allowance (kg DM/day)     Estimate of maximum intake + 20% for wastage

Steers or unjoined heifers               300kg grown to 400kg at sale

Mature cows (British breed)            500kg, fat score 2.5–3.0

kg DM/ha = kilograms of dry matter per hectare
MJ ME/kg DM = megajoules of metabolisable energy per kilogram of dry matter

The tables below provide further estimations for use in calculating the important components of managing the grazing system.

The Feed Demand Calculator available on the MLA website will help you calculate the appropriate stocking rate and length of paddock rotation.

Step 1: How much pasture is available for cattle to graze?

This involves estimating the ‘grazing opportunity’ in kilograms dry matter per hectare (kg/DM/ha) by assessing pasture height and related density using the MLA Pasture Ruler or equivalent measurement tool. Refer to MLA Tip & Tool: Improving pasture use with the MLA Pasture Ruler for information on how to use the MLA Pasture Ruler to convert the height of a moderately dense pasture into an accurate estimate of kilograms of green dry matter per hectare.

In practice, the conversion of pasture into beef product is greatest when the paddock grazing sequences ensure:

  • The most appropriate class of cattle is used to meet production targets.
  • Pasture energy supply matches animal energy demand.
  • Pasture mass is maintained in a green, leafy and vegetative condition across the paddock at 1,500–2,500kg green DM/ha (around 6–12cm high) and with the recommended number of live leaves and tillers for the grazing period.
  • The number of animals allocated for grazing enables accurate prediction of the grazing period, while maintaining pasture mass above 1,000kg green DM/ha (3cm high) to ensure rapid regrowth and to prevent grazing of new growth.

An estimate is needed of how much pasture is wasted through animals trampling and fouling during grazing. Around 20% wastage is a reasonable estimate and is used in the worked examples.

Step 2: What pasture allowance is required for various classes of grazing cattle?

Pasture allowance is described as food needed for growth and maintenance of the stock (intake) plus an allowance (20%) for trampling and fouling. Pasture allowance is based on a pasture of at least 10MJ ME/kg DM and is not applicable to pastures of lesser quality.

Table 1: Guide to pasture allowance for steers and unjoined heifers, at a range of weights, grazing pasture of at least 10MJ ME/kg
Liveweight (kg) 200 300 400 500
Pasture allowance
(kg DM/head/day)
8 10 12 12

 

As an example, a 300kg steer or heifer requires a pasture allowance of 10kg DM/day to achieve potential animal growth from pasture quality of 10MJ ME/kg DM.

Table 2: Guide to pasture allowance for 500kg cows in different physiological conditions
Mature British breed cows
(500kg, fat score 2.5–3.0)
Dry/late pregnant Early lactation* (2 months) Lactating* (5 months)
Pasture allowance
(kg DM/head/day)
10 15 20
* Includes an allowance for calf

As an example, a 500kg cow, fat score 2.5–3.0 in early lactation requires a pasture allowance of 15kg DM/day.

Table 3: Average daily gain for a range of feed quality and steer liveweights

Open PDF

average-daily-gain-for-feed-quality.png

ADG = average daily gain
Source: calculated using GrazFeed v 4.1.5

The following assumptions are used

  1. The weights and ages are 200kg at 9 months; 300kg at 18 months; 400kg at 24 months; and 500kg at 30 months.
  2. Breed type is British (Angus, Hereford, Shorthorn, etc.) and their crosses.
  3. Mature weight of cows of same breed type 500kg.
  4. There is no cold stress.
  5. Pastures are manipulated for the calculation by setting dead material at 5% for 12.0, 10.5 and 9.0MJ ME/Kg DM (M/D) and green at 1% for 7.5 and 6.0MJ ME/kg DM (M/D).  The availability refers to amount present in the major component, eg MJ ME/kg DM 10.5 (or M/D 10.5).  The green component was varied from 1.0, 1.5, 2.0, 2.5, 3.0t DM/ha.

Step 3: Calculate the stocking rate over short grazing periods

Follow the example to calculate the stocking rate for a 2,500kg green DM/ha pasture with a nutritional quality of ME >10.5MJ/kg DM for 300kg steers growing at 1kg/day.

Example for 1 day grazing

Information for calculation:

  • Pasture at start of grazing             2,500kg DM/ha
  • Pasture at end of grazing              1,500kg DM/ha
  • Pasture allowance (PA)                10kg DM/day/steer (see Table 2)
  • Number of grazing days                1 day

To estimate use the formula:

Animals/ha = (pasture mass at start of graze – pasture mass at end of graze) / pasture allowance

Animals/ha = (2,500kg DM/ha – 1,500kg DM/ha) ÷ 10kg DM/day/steer PA = 100

Answer: 100 steers/ha for 1 day grazing 

Example for 5 days grazing

Grazing a pasture of the same quantity and quality for 5 days:

100 steers/ha ÷ 5 days grazing = 20

Answer: = 20 steers/ha stocking rate

Note: When calculating the short-term stock numbers while using short-term, high density grazing (1–5 days), there is no need to make an allowance for any pasture growth.

When grazing pasture for longer periods, an allowance needs to be made for the expected pasture growth during the grazing period. As a guide to mid-monthly pasture growth estimates, refer to Tool 3.3 for estimates of daily pasture growth rates (kg DM/ha/day) for typical conditions in a range of localities and regions across southern Australia.

Calculate the stocking rate over short grazing periods
kg DM/ha
kg DM/ha
DM/ha/day
DM/day/steer
day

steers/ha

Note: When calculating the short-term stock numbers while using short-term, high density grazing (from 1 to 5 days), there is no need to make an allowance for any pasture growth.

When grazing pasture for longer periods, an allowance needs to be made for the expected pasture growth during the grazing period. As a guide to mid-monthly pasture growth estimates, refer to Tool 3.3 for estimates of daily pasture growth rates (kg DM/ha/day) for typical conditions in a range of localities and regions across southern Australia.

Step 4: Determine the stocking rate/hectare over longer grazing periods

The big challenge in grazing management is being able to predict the stocking rate that takes advantage of any period of rapid feed growth. The question to be answered is “How many cattle are required to achieve the combination of productivity and profitability?”. MLA's Stocking Rate Calculator along with the Feed Demand Calculator can help you calculate the appropriate stocking rate for the nominated grazing period. Both calculators are available online from http://www.mla.com.au

In this example, the stocking rate/ha (for number of days grazing) is estimated by the calculation:

(pasture mass at start of graze – pasture mass at end of graze) + (pasture growth rate × number of days intending to graze paddock) ÷ (pasture allowance × number of days intending to graze paddock)

Information for calculation:

  • Pasture at start of grazing             2,500kg DM/ha
  • Pasture at end of grazing              1,500kg DM/ha
  • Pasture growth rate (PGR)           30kg DM/ha/d (see Tool 4.3 for state regions)
  • Pasture allowance (PA)                10kg DM/day/steer  
  • Number of grazing days                7 days

To estimate use the formula:

Stocking rate = [(pasture at start of graze – pasture at end of graze) + (PGR × number of graze days)] ÷ (PA × number of graze days)

Example for 300kg steers or unjoined heifers for 7 days grazing

Where the estimated pasture mass at the start of grazing is 2,500kg DM/ha and expected end of grazing pasture mass is 1,500kg DM/ha, pasture growth rate is expected to be 30kg DM/ha/day and the pasture allowance is 10kg DM/day.

(2,500 – 1,500) + (30 × 7) ÷ (10 ×:7) = 17

Answer: The stocking rate for the 300kg steers is 17 steers/ha for 7 days grazing

This calculation is suited to a wider application and can be applied to many different pasture and grazing scenarios and stock classes.

Example using the same pasture information for cows in early lactation for 30 days grazing

Information for calculation:

  • Pasture at start of grazing             2,500kg DM/ha
  • Pasture at end of grazing              1,500kg DM/ha
  • Pasture growth rate (PGR)           30kg DM/ha/day (see Tool 4.3 for regions)
  • Pasture allowance (PA)                15kg DM/day/steer
  • Number of grazing days                30 days

To estimate use the formula:

Stocking rate = (pasture at start of graze – pasture at end of graze) + (PGR × number of graze days) ÷ (PA × number of graze days)

Stocking rate = (2,500 – 1,500) + (30 × 30) ÷ (15 × 30) = 4.2

Answer: The stocking rate for lactating cows = 4.2 cows/ha for 30 days

In this example, a 30ha paddock with a pasture growth rate of 30kg/ha/day is capable of running (30ha x 4/ha) = 120 cows for 30 days; and a 50ha paddock could run 200 cows for 30 days.

Example for a 3-day rotational grazing system

Use the same calculation for the 30-day example applied to a 3-day grazing rotation to work out the stocking rate for lactating cows:

Stocking rate = (2,500 – 1,500 + 0 for pasture regrowth) ÷ (15 × 3) = 22

Answer: Stocking rate 22 cows/ha

A 10ha paddock is capable of running 220 cows (10ha x 22/ha) for the 3-day grazing period in the rotation.

A 30ha paddock with nil pasture regrowth is capable of running 660 cows (30ha × 22/ha) for 3 days and a 50ha paddock could run 1,100 cows for 3 days grazing.

Plan seasonal pasture and animal performance to achieve targets

Information required for the calculation:

  • Average pasture growth rate over the season
  • Number of grazing days

Be sure to make adjustments to suit the local seasonal and pasture growth conditions:

  • In dry seasons, reduce the estimate of kg DM/ha/day, in drought years good soil fertility will have a positive impact on amount of pasture grown.
  • Adjust estimates according to the growing conditions, pasture density or when there is more than 30% bare ground.

Step 1: Calculate the accumulated pasture growth over the season

Example for calculating the total pasture growth

Information for calculation:

  • Average pasture growth rate         40kg DM/ha/day (see Tool 4.3 for regions)
  • Number of grazing days                100 days

In this example, there is an average pasture growth rate of 40kg DM/ha/day for 100 days for a normal spring season in southern Australia. Refer to Tool 3.3 for a guide to the daily mid-monthly pasture growth estimates (kg DM/ha/day) for typical conditions at a range of localities and regions.

The estimate of total pasture growth is 40 × 100 = 4,000kg DM/ha

Answer: 4,000kg DM/ha (growth over 100 days)

Step 2. Calculate the number of grazing animals required/ha

Example for calculating the number of grazing animals required

Information for calculation:

  • Total pasture growth                      4,000kg DM/ha (Step1 – total pasture growth calculation)
  • Pasture allowance                         10kg DM/day/steer
  • Number of grazing days                100 days

To estimate use the formula:

Number of animals = pasture growth ÷ (pasture allowance × no. of days grazing)

A herd of 300kg steers with an estimated 4,000kg DM/ha total growth over the 100 days spring growth and a pasture allowance of 10kg DM/head.

Number of animals = 4,000 ÷ (10 x 100) = 4

Answer: Number of animals = 4 animals /hectare

In this example, 120 animals (4 animals/ha × 30ha) are required in a 30ha paddock to have the same amount of pasture mass at the start and finish of grazing through 100 days of pasture growing at 40kg DM/ha/day.

Step 3. Estimate the stock growth rate and weight gain (kg/head/day)

Example for estimating growth in 300kg growing steers or unjoined heifers in 100 days grazing

Information for calculation:

  • Steer liveweight at start                300kg
  • Pasture at start of grazing            2,500kg DM/ha
  • Pasture growth rate                      30kg DM/ha/day (see Tool 4.3 for regions)
  • Quality of feed                               10.5MJ ME/kg DM
  • Average daily gain                        0.98kg/day (or approximately 1kg/day – see Table 3*)
  • Number of grazing days               100 days

Answer: In 100 days grazing expected weight gain is 100kg liveweight/head

Calculating the gross financial benefit/hectare to the grazing business

Once you have an estimate of the stocking rate and the number of days that stock will be grazing the pasture to achieve the target weight gain, the gross return per hectare can be calculated.

Example for calculating gross financial benefit

Information for calculation:

  • Purchase price                             $600 (300kg × $2/kg)
  • Sale price                                      $760 (400kg × $1.90)
  • Difference sale and purchase    $160 ($760 – $600)

To estimate use the formula:

Gross financial benefit = number of cattle per hectare × (purchase price less sale price)

Answer: At a stocking rate of 4 steers/ha × $160, the estimated gross return is $640/ha

Note: This is simply the gross financial benefit to the grazing business. The operating costs need to be deducted to arrive at an estimated gross margin.