Matching stocking rates with available forage ensures animals always have sufficient feed. This minimises the impact of dry years and drought feeding costs. Most importantly, it prevents overgrazing and reduces the impact of drought on land condition.
Conversely, in good years stocking rates can be adjusted upwards to increase production without damaging pastures. This maximises animal production and productivity while maintaining land condition in our variable rainfall environment.
When stocking rates are not matched with available forage, overgrazing occurs and land condition declines. Indicators that this is occurring include:
• low ground cover (<50%) at the end of the dry season
• ground cover consistently lower than regional averages for the land types, especially in dry years (see FORAGE online tool)
• pastures dominated by unpalatable species like wiregrass, annual grasses and/or forbs
• high runoff with break of season storms and reduced response to rain.
Evidence from the MLA-DAF funded Wambiana grazing trial near Charters Towers shows failure to reduce stocking rates in dry years results in reduced animal production and pasture degradation.
This can occur even if stocked around the long-term carrying capacity (LTCC). These effects are even more marked if stocked above the LTCC, as demonstrated in the heavy stocking rate paddocks at the trial.
Conversely, adjusting stocking rates to match available forage reduced the impact of dry years and maximised the benefits of better seasons. It increased drought resilience and was more profitable due to lower costs (especially by avoiding drought feeding) under a gross margin analysis.
The Ecograze trial near Charters Towers also showed that adjusting stocking rates to achieve the recommended pasture utilisation rate of 20-30% maintained land in good condition in drought years and allowed land in poor condition to improve.
However, the Wambiana trial showed overstocking in good years and/or failing to cut numbers sufficiently fast as drought approaches can result in long-term damage to land condition. Stocking rates must thus always be adjusted with caution as discussed below.
The primary stocking rate adjustment point should be around the end of the wet season, as this is when there is the greatest certainty about how much forage will be available for the year (i.e. there is little chance of further growth) and how long it has to last (i.e. the 6 to 8-month dry season).
Other logical secondary stocking rate adjustment points are in the mid and late dry season and in the early to mid-wet season.
Adjust stocking rates in a cautious, flexible manner as seasons vary, based on available forage, animal performance and seasonal conditions.
Where appropriate (i.e. later in the dry season when accuracy is highest), climate forecasts should also be taken into account—particularly when an El Nino is forecast.
Stocking rates are usually set based on a forage budget. This is done by first estimating the amount of feed in a paddock based on photo standards or some other method (see ‘Tools and resources’ section).
Where tree cover is low, satellite-based tools can also be very helpful.
A calculation is then done to estimate the number of animals a paddock can support for a defined period of time (the dry season plus a buffer) as explained later in this document.
The flow diagram shown in Figure 2 lays the process out in a series of easy steps.
Other useful means of adjusting stocking rates are:
Even if not running a rotational grazing system, regularly calculating grazing days per hectare in relation to rainfall is a very good way of keeping check on stocking rates relative to seasonal conditions.
Whatever the method used, it is important to set upper limits on stocking rates in even the best seasons to prevent overgrazing. As an example, never more than 20% above LTCC.
Changes in stocking rate should always minimise risk i.e. cut stocking rates sharply (e.g. by 20-40% or more) with the approach of poor seasons but increase stocking rates gradually (e.g. 10-15%) during good seasons. The degree of change will also depend on:
Remember: Stocking rates based on forage budget estimates are only broad guides — use with caution and adjust numbers as needed.
Aside from the primary decision point at the end of the wet season, it is also important to:
Click here to enlarge the balancing stock numbers with forage availability decision tree.
To learn how to do a forage budget attend a Stocktake forage budgeting course and/or use the Stocktake App (see ‘Tools and resources’).
To do a forage budget, you need to know the following:
Forage budgeting calculations take the forage available to the animal and subtract the desired residual amount after grazing to give the total useful available pasture. This figure is used to determine how many animals can run in a paddock for a certain period of time. The time can be manipulated either way (e.g. more cattle for a shorter time or a sustainable number for the whole dry season).
Calculations can be complex and will be detrimental to land condition and production if too optimistic. It is therefore recommended to seek assistance from an extension officer.
Alternatively:
For more information contact your local extension officer.
The ‘usual’ start of the wet season growth is taken as the date when there is >75 % probability of getting more than 50 mm of rain in two days (i.e. later than the ‘green date’ date’). Always add a buffer of at least a month in case of a late start.
The Wambiana trial is co-funded by the Department of Agriculture and Fisheries and Meat and Livestock Australia.
