Developing a proper stocking rate is among the most important practices a manager can accomplish. No fertilization plan, brush management plan, rotational grazing plan or herd genetic selection can overcome overgrazing from a continually high stocking rate. While short-term financial gains might be seen from overstocking pastures, long-term financial and ecological sustainability is not feasible while overgrazing.
Stocking rates are developed by balancing livestock numbers with the forage available for the animals to consume. There are several ways this is accomplished. A range and pasture consultant will use production estimates from clip sampling forages, the soil's production potential, species composition, plant health and vigor, and grazeable acres in each pasture to determine the amount of forage available in addition to animal demand to estimate an initial stocking rate. This estimated stocking rate is based on the current health of the grazing land and a normal year of rainfall. It attempts to balance animal demand with the forecasted forage production for the upcoming growing season.
As you can imagine, this forecast is very dependent on the weather and thus very dynamic. The stocking rate will also need to be dynamic. Adjustments will need to be made to match the actual forage production. Implementing a monitoring plan gives grazing mangers the information they need to make timely decisions on stocking rates. Timely decision-making is a trait shared by the most successful grazing managers.
Grazing exclusion cages are just one component of an effective monitoring plan. A monitoring plan gives timely information to manage a grazing plan and also helps the grazing manager learn how vegetation, grazing animals and rainfall interact with one another, and what changes those interactions will cause across the landscape. Mangers must monitor and document changes to ensure management is not causing damage to soil and plant communities and to evaluate whether or not past actions are producing desired results. Managers who are dedicated to improving the quality of their pastures will ultimately see results in profitability, with economic and environmental changes that benefit the sustainability of their business.
Grazing Exclusion Cages: A Tool for Monitoring Forage Production
Grazing exclusion cages are one of the most effective tools for observing grazing utilization within a monitoring plan. The cages exclude grazing animals from a small representative area so that grazed vegetation outside the cage can be compared to ungrazed vegetation inside.
Why use cages
Cages give timely and intuitive information on grazing use that can be used to adjust stocking rates or make changes to a rotational grazing plan. Overutilization is an indication that a pasture could be overstocked. For more in-depth monitoring, forage production can be measured inside the cage and compared to production outside.
How to construct cages
The cages can be constructed by bending welded wire cattle panels at 90 degree angles and combining two panels to form a square. A T-post can be driven at all four corners and attached to the panels to anchor them in place. For a simpler cage, one panel could also be bent around on itself and a T-post used as an anchor where the two ends meet with another post on the opposite side of the ring. This will result in a teardrop shape.
Cage size
Cages should be large enough that forage production measurements can be collected at multiple times during the growing season and then again after frost. A 2-meter-by-2-meter cage will give enough room to sample at least four times during the year.
Where to place cages
Cages should be placed on key sites that are representative of the entire pasture. Make sure they are not in high-use areas or so far away from water that use is limited.
What to observe
Visually monitor the cages periodically to determine grazing utilization. In native rangeland pastures, no more than 50 percent of the leaf area of plants available for grazing should be consumed, stomped down, urinated on or otherwise utilized.
How to gain information
Compare the monthly or seasonal forage production to forecasted production to make timely decisions to balance forage production and animal demand. The ungrazed/unsampled forage inside the cage after frost is the total production for the growing season. Compare total yearly production to the expected production and to production from previous years, relative to rainfall amounts, to help determine if grazing land health is increasing, decreasing or stable.
How to reuse for next year
Cages should be moved to a new area within the key site every winter. Previous season growth should be removed inside the cage to ensure it is not included in sampling the upcoming growing season's production.
