The Cow-Calf Manager

Livestock Update, September 2007

Dr. John B. Hall, Extension Beef Cattle Specialist, VA Tech

Grazing Management Crucial During and After Drought

All of Virginia is still in a drought which varies from mild to severe depending on location.  In some areas of the state recent rains have pushed the grass along and we are finally seeing some decent grass growth.  However, most of Virginia appears to be in a continuing and deepening drought.

How pastures are managed over the next couple of months will dictate how much grazing is available this fall, and whether we will be able to meet the nutritional needs of our cattle.  In addition, this grazing management will also impact how well pastures will survive the winter.

Pasture growth

 We need to remember that pastures grow above and below ground.  During droughts like we’ve had this spring and summer not only has there been very little to graze on top, but the constant defoliation has reduced the amount of roots our pastures have as well.  As the top of the plant grows and makes energy from the sun, it uses some of that energy to make more roots so it can get more nutrients and water.  During severe grazing or drought some of the grass and legume roots die because there is not enough energy to sustain them.  Also the plant will use some of its root reserves to grow more leaves during times of drought or severe grazing.  If the severe grazing or drought continues long enough the plants die or become weak.  That’s why we have more bare ground in our Virginia pastures right now.  In addition, weakened plants will not be able to survive the winter, especially if it is cold and dry.

Figure 1.  Impact on grazing height on re-growth and root mass.

It is important when we graze cattle that we don’t let them graze the grass too short.  Sufficient leaf area must be left on the plants for rapid re-growth and increase root growth.  In most cases, producers should leave 2 – 4 inches of plant height in the pasture.  Figure 1 illustrates the differences in re-growth from well-grazed verses overgrazed pasture.  Optimum grazing height will depend on the primary grass species.  Suggested amounts of forage to leave are: 4 inches for orchardgrass and fescue, 2 inches for bluegrass, 1 to 2 inches for bermudagrass.

Proper grazing with a rest period will allow plants to develop more tillers and roots.  Figure 2 illustrates the results from an experiment conducted at Virginia Tech several years ago by Dr. Roy Blaser.  Grass plants were either grazed then rested (two plants on left) or continuously grazed (two plants on right).  Then the plants were either grazed severely or grazed properly.  The properly grazed plants that had a rest between grazing grew faster, had more roots and produced more tillers.  So these plants made a healthier pasture.  Most of our pastures look like the overgrazed plants on the right; they have few roots and are making few tillers.

Figure 2.  Effect of rest period and grazing height on regrowth, tillers and roots.

Since VA pastures are in this fragile state over-grazing and dry weather in the next month or two could really hurt the possibilities for decent pasture for the rest of the year (if we get fall rains) and could permanently damage pasture.  Proper grazing will also allow for better and earlier growth next spring which will be important in this short hay year.

Grazing Management and Nutritional Needs of the Cow

Since we know we need to give our pastures a little break, how do we manage them for the next two months and even into the winter?  It is critical that pastures are allowed to develop enough top growth to recover and build-up reserves for winter as well as be able to take advantage of fall rain.

Most of Virginia drought stressed pastures are not supporting the nutritional needs of the cow and calf.  Therefore, supplementary feeding is going to be required in order to keep cows from losing too much weight.  The Cow-Calf Manager articles from the past few months discussed the advantages of early weaning and culling non-productive cows.  Now let’s focus on grazing strategies.

Strategy 1 – Sacrifice one pasture to let the others recover.  This may be the easiest and best strategy for most operations.  Continuing to feed hay in one pasture while allowing the other pastures to get to 6 to 8 inches of growth before grazing allows pastures to recover and build reserves.  Then only graze down to 4 inches before returning to the sacrifice pasture.  This will cause some damage to the one pasture, but it will allow the other pastures to recover from drought.

For an operation with one big pasture, putting up three to four strands of high tensile electric fence with a portable charger is a method for creating a sacrifice pasture.

Strategy 2 – Keep them full and limit access to pasture.  Cows will usually eat until they are full, so they will continue to graze the young growth even though they are getting more nutrition than they need.  Keeping a round bale available at all times will help fill cows up and reduce some of their grazing pressure.  Another method is to put them out on pasture for only 12 hours and bring them off the pasture with a by-product feed and into an area where a round bale is available.  While this may be the only option for operations with one big boundary, this strategy actually does little to enhance pasture regrowth.

Strategy 3 - Use Multiple pastures and move fast.  The idea is to allow pastures to make 6 to 12 inches of growth then graze the top leaving 4 to 8 inches, then move to the next pasture.  You will need 4 to 6 pastures to do this, but you can make the divisions out of temporary electric fence.  Don’t leave cattle in any pasture for more than one week.  This option is for the few areas of the state that received significant rainfall recently.

A combination of these strategies is probably the most effective, but producers need to decide what works for each operation.  Producers that are willing to employ grazing management in late summer and early fall will be rewarded with healthier cattle, more fall grazing, and stronger spring pastures.

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