The Cow-Calf Manager:
Grazing Management Crucial After a Drought
Livestock Update, April 2000
John B. Hall, Extension Animal Scientist, Beef, Virginia Tech
Most of Virginia has received 1.5 to 2.5 inches of rain in the last 2 weeks. The warm spring along with the rain has pushed the grass along and we are finally seeing some decent grass growth. While some of Virginia east of the Blue Ridge had a good fall with considerable forage growth, other areas like Southwest Virginia continued to have drought conditions. Even the best looking pastures are still in a weakened condition after 2 years of drought and heavy grazing.
How we manage our pastures over the next few weeks will dictate how much feed we will have the rest of the summer, and whether we will be able to meet the nutritional needs of our cattle. In addition, this grazing management will also impact how are pasture will hold-up should we have another dry summer as predicted.
We need to remember that pastures grow above and below ground. During droughts like we've had the last two years 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 after the last two years.
It is important when we graze cattle that we don't let them graze the grass too short. We need to keep enough leaves on the plants for rapid regrowth and increase root growth. We need to leave 2 to 4 inches of plant height in our pastures. Figure 1 illustrates the differences in regrowth from well-grazed verses overgrazed pasture.
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 our pastures are in this fragile state over-grazing or dry weather in the next month or two could really hurt the possibilities for decent pasture for the rest of the 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? This is one year when we actually want the pasture to get a little ahead of us. First, I hope you got a chance to frostseed or overseed your pastures in late winter. Second, fertilizing pastures this spring will be beneficial to pasture recovery. Third, grazing management is important.
Remember that the grass that is growing now far exceeds the protein and energy needs of the cow, so if allowed to eat all she can she will gain weight. That may be a good thing, but early on if she overgrazes she will hurt the stand. We can essentially use the pasture as a supplement for hay or other forages.
Strategy 1 - 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.
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 corn into an area where a round bale is available.
Strategy 3 - Sacrifice one pasture to let the others recover. Continuing to feed hay in one pasture while allowing the other pastures to get to 6 to 8 inches of growth before grazing. This will cause some damage to the one pasture, but it will allow the other pastures to recover from last years drought. This may be the easiest strategy for most of us.
A combination of these strategies is probably the most effective, but you have to decide what works for you.
Since we are want to allow the pastures to get ahead of us this year, producers will have to make sure they adopt some addition pasture management in late May and early June like making hay off some pastures that are usually grazed. In addition, cows may need some supplement while they graze down pastures that have become a little rank.
Pasture management will be a little tricky this spring depending on rainfall. They key is not over graze developing pastures and leave at least 4 inches pasture available to strengthen the pasture. This means you need at least 4 pastures or paddocks for rotational grazing. If you graze properly now you will have more grass in June, July, and August. In addition your pasture will be better able to with stand a drought.