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OSU Extension

College of Food, Agricultural, and Environmental Sciences

May 12, 2020 - 8:00am --

Like any resource, pastures respond to management.  Grazing offers economic benefits as compared to producing and feeding stored forages as livestock harvest the forage directly. Capture the benefits of grazing and set yourself up for success by using the 4-R’s to manage pastures.  We typically hear of the 4-R’s in relationship to water quality and fertilizer management, but pasture management has its own set of 4-R’s.  Those 4-R’s stand for the grazing principles of Right beginning grazing height, Remove/Reduce seed heads, Residual leaf area, and Rest period.

Do not begin to graze pastures too soon.  There is a positive correlation between pasture plant height, density, and livestock intake.  Animal intake is directly correlated with animal performance.  The goal is to make sure that grazing livestock get a full mouthful of forage with every bite they take.  For example, cattle on average graze for 8 hours/day, averaging 30,000 total bites.  If the pasture growth is too short and they only get a partially filled mouth of forage in every bite, they do not make up for it by grazing longer or taking more bites.  Total forage intake will be lower compared to the cow able to get a full mouthful in every one of her grazing bites.  In general, after the spring growth flush, plan to start grazing when pastures have 8-10 inches of growth.

In the spring through early summer, our cool-season grass plants will shift from vegetative to reproductive growth and produce seed heads.  When this happens, the grass plant no longer produces new vegetative tillers and the nutritive quality of the plant decreases. Removing or reducing seed head production by mowing/clipping or providing heavier stocking density and grazing pressure will keep pastures more productive. Removing the seed head returns the plant to vegetative growth.

 After a grazing pass, plant regrowth will come from carbohydrates produced by remaining leaf area through photosynthesis or from carbohydrates mobilized from root reserves. Overgrazing is the bane of pasture productivity because it demands that much of the regrowth will draw upon carbohydrate root reserves.  Additionally, overgrazing significantly reduces root mass and volume, further delaying plant recovery after grazing.  Residual leaf management is an important grazing principle to maintain pasture health, quicker regrowth, and more total forage production.  The goal is to remove livestock when there is still 3-4 inches of pasture growth left.  In grazing schools, we sometimes say, “take half, leave half” to illustrate this principle.  Leaving this amount of leaf residual allows the plant to continue to produce carbohydrates through photosynthesis and results in more rapid plant recovery and regrowth, without drawing down plant root reserves.

The final management piece is rest period.  The rest period is the recovery time that allows a plant to grow back to the target beginning grazing height.  The length of time necessary for this to happen depends upon weather conditions and how that plant has been managed in the past.  In general, rest periods between grazing passes may vary from 15-20 days in the spring to 30-40 days in the summer.  If conditions turn hot and dry, longer rest periods are required.

The 4-R’s of grazing involves a system approach and is all about protecting the pasture plant and making sure it thrives.  When pasture plants thrive, grazing livestock benefit.  The goal is to avoid a situation where a plant is overgrazed and/or where a plant is grazed too soon after a grazing pass.  This situation leads to plants that draw down or deplete root reserves, resulting in weak plants that struggle to regrow and that may disappear from the pasture mix if the practice continues repeatedly. 

The only way to manage pastures and follow the 4 R’s of grazing is through pasture divisions.  The successful grazier needs at least 8 to 10 pasture paddocks to have the flexibility to vary pasture rest periods from 15 to 40 days.  Pasture productivity, grazing success, is multiplied by dividing pasture grazing area.  More divisions are better than fewer.  I know graziers who have used 20, 30 even 40 pasture divisions.  I have never heard one of them say that they overdid it and had too many divisions. 

Another benefit of more pasture divisions is that they allow the livestock manager to put more head in a smaller area.  This increases stocking density.  When stocking density increases animal selectivity decreases, resulting in more uniform grazing.  Additionally, manure distribution, and thus nutrient recycling, is more uniform as pasture divisions become smaller and stocking density increases.

Pastures respond to management.  Plant fence posts and increase grazing success by using the 4-R’s of pasture management.


Rory Lewandowski is an OSU Extension Agriculture & Natural Resources Educator and may be reached at 330-264-8722.


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