Fine Tuning Rotation

The simulation of pasture grazing can be flexed to provide more than a single grazing rotation based on tight pasture cover parameters.

By testing different scenarios based on practical experience you can gain a better understanding of your farm's characteristics and identify opportunities for improved grazing production from minor shifts in the grazing parameters used by your simulation model.

1. Setting Pasture Parameters.

Threshold Cover – The target minimum grazing level set at different levels according to the season and your expected rate of daily growth rate objectives from hard or lax grazing policies or winter stock feeding policies.
Maximum Grazing Cover – This upper limit set of the grazing band cover is limited by the twin problems of pasture quality and declining daily growth rates.
Residual Mowing Cover – The cover remaining after mowing for harvesting or topping.
Minimum Harvesting Cover – This is the cover level that triggers the auto harvesting point. This input can be set higher to leave paddocks aside for “fixed herd in paddock” feeding option or for rotations with some mobs on a rotation based on selecting paddocks with highest cover.
Median Cover – This is the cover level where the daily growth rate peaks and starts to decline. The input will differ between farms due to different pasture composition and different past pasture management policies.

Pasture parameters must be set with the physical reality of your farm in mind. If on your 100 Ha, 20 paddock, 275 cow farm you feed 20kg/dm/cow/day (5500/5=1100) your feeding band must be wider than 1100kg of cover.

For example, if your threshold is 1500kg, maximum grazing cover must be greater than 2600kg (2600-1500=1100). More importantly, the grazing band must be greater than 1100kg to allow for paddock variability in the selection process over time, otherwise on some days there could be no paddocks meeting the selection criteria.

The growth formula used by shows that total cover has a significant bearing on the daily growth rate of individual paddocks. The positioning of the grazing band around the median cover setting can vary your farms average daily growth rates significantly. However, pasture quality in the grazing band becomes more difficult to maintain the higher the band is set.

There are circumstances where reduced daily stock intakes are planned. The threshold level must be reduced to a realistic level that matches you herd's willingness to closely graze when on restricted pasture.

2. Stock & Policies

By using a combination of 12hr or 24 hr rotation base and choosing a feeding policy for each herd or stock class a wide range of rotation options can be produced

12hr and 24hr Rotation – This choice enables you to better match your farms level of subdivision to the modelling system.
Feeding Policy:
1. Matching Requirements to Threshold – Selects the paddock with the closest fit to your threshold grazing cover. This means that in times of growth exceeding consumption paddocks will grow through to harvesting covers. Conversely in times of lower growth than consumption the model will run out of feed and stop. The remedy is to lower the daily amount fed to herds and raise the level of supplementation, lower the threshold level or raise the maximum grazing level or a combination of all these.
2. Grazing to Threshold – Selects the paddock with the highest cover less than the maximum grazing cover and retains the stock in the paddock until the threshold cover is reached.
3. Find Highest Cover – Selects the paddock with the highest cover less than the maximum grazing cover and retains the stock in that paddock according to the 12hr or 24hr rotation setting and until the cover level is lower than the next highest paddock cover on the farm.
4. Herd Allocation to Paddock – Enables individual herds to be allocated to specific paddocks which provides additional options when used in conjunction with policies.
5. On multi herd farms with a range of paddock sizes, unequal sized herds selecting from all paddocks, will enable the simulation to select a rotation plan that more closely fits the planned grazing threshold after grazing as a result of having available a wider range of matching variables for selection from each day.

3. Harvested Feed Data

Harvest Yield – Sets the net yield of pasture available that is actually stored.
Harvest Period – This sets the period and the form of harvesting of paddocks whose covers exceed the minimum harvesting level in the course of a simulation run. These harvest periods must not overlap and should only be in place for those periods of the year when harvesting is practical.

4. Growth Rates

The growth rate entered into the projected average growth rate table is just that, a composite of all the daily paddock growth rates from your entire farm.

A rotationally grazed farm has all paddocks at different stages of recovery from an earlier grazing.

Therefore, the range of individual paddock daily growth rates will range either side of the average growth rate as a result of the variance in time from last grazing.

In addition to the effects of time from grazing on daily growth rates, provision is made for the variation of individual paddocks daily growth rates by 10% up or down. This “Paddock Growth Variance” enables you to allow for paddocks that are more or less fertile, wetter or dryer, new or old pasture, warm or cold aspects as you enter your paddocks data in the Paddocks page.

5. Pasture Utilisation

No provision has been made for variable feed utilisation caused by the actions of the grazing animal at time of grazing.

There are two primary causes of feed loss at grazing:

Harvesting loss - The feed that is spilled by the animal in the act of harvesting the pasture.
Soiling and treading loss - The feed that becomes unpalatable as a result of wind, rain and cold causing the herd or mob to congregate, tread, churn and muddy pasture under poor climatic conditions.

Experience will show that provision for lower utilisation can be made by increasing the daily amount of pasture provided in the model. By increasing the daily pasture drymatter by 10 to 20 percent in periods of wet and cold to cover soiling and treading or 5 to 10 percent to cover harvesting losses a more realistic result may be obtained.

6. Summary

is a modelling system which not only provides a feed plan , but through its use, gives the farm manager an structured insight into the complexities of pasture production and consumption. This insight is based on growth measurements that are specific to your farm.

is therefore more than a management tool and by simulating, trialling and refining different grazing scenarios for each season it invites the farm manager to gain a better understanding of the dynamics of pastoral farming.