Roger Gates: Winter grazing requires prudent planning
November 3, 2011
Ice on the windshield is a reminder that winter is growing closer. I wrote last time about the value of assessing pasture utilization that had resulted at the end of the growing season. That information is essential to evaluating whether or not your goals for this year’s grazing plan were achieved. In short-hand it answers the question, “did whucha did, do whucha wanted?”
Another end-of-season assessment that should guide grazing plans is the condition of pastures stockpiled for winter grazing. Good growing conditions in the Northern Plains combined with the demand for feed in the Southern Plains have resulted in substantial export of hay from our area to the south. When combined with continued high rates of corn disappearance, market factors will keep costs for supplemental feeds high.
Decisions about winter grazing should consider at least two aspects – the nutritional needs of the livestock and stewardship of resources.
Nutrient content of dormant forage is generally adequate, especially for the needs of a mature, dry cow. Recently weaned, growing animals have higher nutritional needs, but even they can be maintained and grow slowly on dormant forage that is allocated appropriately.
If the rationale for winter grazing is to limit costs, then expenditures for supplemental feed should be minimized. Protein is likely to be the first limiting nutrient in dormant pasture. Needs for supplementation will increase as nutrient demands increase, particularly for a pregnant female.
Testing the nutrient content of the vegetation animals are selecting provides the best guidelines for determining needs for supplementation. One challenge in evaluating nutrients available from dormant pasture is anticipating how the season’s growing conditions might influence nutrient concentrations.
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The past growing season provided nearly ideal growing conditions for pasture plants. It might appear logical that nutrient content of the plants would also be favorable. However, the opportunity for plants to fully mature may actually reduce the available forage quality. Last year was similarly conducive to plant growth. I visited with more than one producer who was puzzled that although the cows were “belly deep in grass” for the summer, weaning weights were somewhat depressed.
Favorable growing conditions allow plants to fully complete their growth cycle. The result is high levels of stem produced and leaves that are very fibrous and lignified. In a drier year, plant development may be arrested, resulting in at least some leaves and stems not fully developed. Less mature plant material is likely to contain higher levels of nutrients.
The most precise way to evaluate nutrient content of winter pasture is to take samples and submit them for testing. Samples should be obtained by “plucking” the plant’s parts likely to be grazed rather than removing the entire plant to ground level.
Plants that are dormant are certainly less susceptible to damage from grazing than actively growing plants. However, careless decisions made during the winter can be just as damaging as any other time.
Since growth has been completed for the year, assessing the forage available for winter grazing is straightforward. The efficiency with which available forage is utilized tends to be lower during the winter, however. Loss of leaves from dry dormant plants from weathering and disturbance is more rapid and severe than for growing plants. Snow cover will also limit harvest of dormant plants.
Areas allocated for winter grazing must therefore be greater than during the growing season; some experts suggest doubling the area. Risks of overgrazing, exceeding the “take half, leave half” rule of thumb, are as important during the winter as any other time. While the plant is not actively growing, the importance of residue in providing thermal protection and maintaining surface structures, such as crown buds, that will initiate growth in the following spring, remains critical.
In addition to appropriate stocking decisions, a rotation plan can be beneficial during the winter, just as it can be during the growing season. Moving to a fresh pasture, even once or twice during winter, better distributes grazing pressure, across more plants and tends to maintain nutrient levels instead of a continuous decline which would occur without rotation. Changing the time a pasture is used provides benefits, even during the winter. Warm spells may stimulate rapid growth of some early season plants. These could be damaged by grazing which occurs at the same time every year. Some plants, such as sedges, which are important to grazing in the early spring, could be damaged by repeated late winter grazing year after year.
Winter grazing requires prudent planning. Provision must be made for adequate water accessibility, protection from severe conditions and contingency for feed provision during blizzards or heavy snow cover. Nonetheless, grazing dormant pastures can provide attractive alternatives to reduce winter feed costs.