Well begun is half done is an old saying that is used to capture the importance of making a thoughtful, planned and managed beginning to a project. That type of beginning can reduce or eliminate later problems, saving time and money. All of this holds true for use of our pasture resource. A good beginning with attention to spring grazing management can help to insure that our summer and fall pasture forages will be more productive. A gross oversimplification of grazing management during the spring period is to minimize seedheads, and rotate through paddocks quickly. Let's take a closer look at the plant physiology behind each of these management directives.
If you think of your pasture as a big solar collector where plant leaves utilize sunlight and turn it into a food product for your cattle, then the goal is to make sure that plant leaves are covering as much of that area as possible. You don't want sunlight hitting bare soil. The vegetative grass plant has the ability to produce tillers that can grow out into bare areas and cover that area with leaves, so keeping a grass plant in a vegetative stage is desirable. However, as day length increases and temperatures warm up in the spring, these conditions act as a physiological trigger that causes plants to shift from vegetative to reproductive growth.
As pasture grass plants shift from vegetative growth in early spring to reproductive growth by mid to late spring there is a decline in forage quality. The reduction in quality is because the reproductive plant produces a fibrous stem that is designed to hold up a seedhead as compared to a vegetative plant that produces leafy tillers. As fiber content increases, forage digestibility decreases, the rate of ruminal passage slows down, intake decreases and animal performance, especially for high nutrient requirement animals like stocker cattle, will decrease. As the seedhead develops a plant hormone is released that inhibits the production of other vegetative tillers. So, for these reasons, an important grazing management principle is to minimize seedheads by clipping or grazing them off. The flower buds that cause seedhead formation are actually initiated on the grass plant under conditions of short daylength and cool temperatures that occur in the fall of the year. New tillers that grow during the spring or summer will remain vegetative. So clipping off seedheads can help to reset the plant into vegetative growth. It is possible that there will be several flushes of seedhead development from a plant until either all the fall initiated flower buds have been released or the day length physiological trigger is no longer present.
Our second spring grazing management directive is to practice a quick paddock rotation. Unless there was an intentional effort to make a change, our pastures are composed of cool season plant species. These plants such as orchardgrass, tall fescue, bluegrass, and white clover to name a few examples, all grow most rapidly under conditions of good moisture and cool to warm temperatures such as we experience in spring through early summer. These species will produce optimum growth at air temperatures of 60 to 75 degrees, with soil temperatures in the 50 to 65 degree range. Because these conditions are common in the spring, we see an explosion of growth. Under these favorable growth conditions a plant recovers rapidly after it is grazed or clipped off. We could see visible regrowth within 24 to 48 hours after grazing or clipping. One of the points that we make in our grazing school workshops is that livestock should not be allowed to re-graze this young growth. There needs to be a recovery period to allow the plant to grow new leaves and replenish any carbohydrate reserves that were used to start new leaf growth following defoliation. What this means in a paddock rotation system is that cattle should not remain in any paddock for more than 2-3 days in spring to minimize damage done to grass plants by re-grazing too soon. The grazing principle is; when grass is growing fast, rotate fast.
The key to making a quick rotation work is to have enough pasture divisions or paddocks to keep cattle moving every couple of days until they can return to the starting paddock where the pasture grass has regrown to 6 to 10 inch height, depending upon the species. Even so, many livestock graziers will drop some of their pasture land out of the grazing rotation in the spring of the year and make hay from it because grass growth is just too fast to manage a complete grazing cycle around the entire area without the forage becoming too mature in those areas that were grazed first. Those areas dropped out of the grazing rotation are worked back in during the summer months when our cool season grass slows down and the grazing rotations need to be extended and slowed down.
Finally, in the midst of spring grazing management take time to look ahead. Those optimum spring growing conditions don't last, and neither does the battle with seedheads, so as a manager you must be prepared for summer. Grass growth will start to slow down and this will impact your rotation plans. For some managers, this means that part of spring management is getting a warm season summer annual crop planted that will be ready for grazing during the summer months when cool season grass growth slows down. Some common options here include millet, sudangrass, and sorghum x sudangrass hybrids. These forage species should be planted when soil temperatures are 60 degrees or warmer. With moisture, these species can be ready for grazing 45 -55 days after planting. These species thrive when air temperatures are in the 85-95 degree range and can produce up to 3 tons of dry matter by that first grazing window.
If grazing throughout the summer months is a goal, its success is set up by good management at the beginning of the grazing season.