Roger Gates: Winter grazing allocation
I had the opportunity to listen to Jim Gerrish on the role of grazing in livestock production at this week’s annual meeting of the South Dakota Grasslands Coalition in Chamberlain. Gerrish drew on his experiences as a producer and researcher in Missouri, his current operation in Idaho and a number of producers who are clients of his consulting business. The last of Gerrish’s presentations focused specifically on winter grazing.
Winter feed represents one of the largest costs for a livestock production enterprise. Grazing pasture that has been stockpiled for winter use is a rational alternative to limit the expense resulting from both harvest (or purchase) and feeding of hay.
Allocation of feed resources available from winter pasture is simplified to one degree because the quantity available can be determined at the beginning of the winter grazing period. The total feed available is entirely dependent on growing conditions during the preceding summer. No additional accumulation of vegetation will occur after a killing frost. Careful observation, supplemented with simple clipping can provide a very reliable estimate of the total feed available.
Unlike grazing plans developed for the growing season, for which uncertainty is substantial because of rainfall variation, the uncertainty associated with winter grazing plans depends on snowfall. Winter grazing may be limited by the duration of open conditions which permit reliable grazing access. However, many producers, determined to make winter grazing part of a year-round grazing goal, have succeeded in providing grazing even when snow cover is substantial.
Winter grazing locations should factor in access to water and protection. Changing the location where vegetation is stockpiled and winter grazed over years can be beneficial to the landscape. No grazing management benefits pasture vegetation as much as deferment for an entire growing season.
Conventional approaches to winter grazing have generally involved turning livestock out in large pastures, anticipating the need to provide a protein supplement, particularly as the season advances and providing hay when snow cover interrupts or finally prevents access to grazing. This procedure may minimize labor and expense early in the winter, but it ignores the opportunity to exploit one of the principle tools available to the manager – animal selection.
Grazing animals have an extraordinary ability to select a highly nutritious diet, even if the average forage quality available is low. By selecting plants and parts of plants that are most palatable, both the energy and protein content of the diet can be considerably better than what the chemical analysis of a clipped forage sample might suggest.
The challenge for the grazing manager is to optimally allocate those “most palatable” components available from the winter pasture. A conventional approach, allocating an entire pasture, allows livestock to select a relatively high-quality diet initially, but the opportunity to select a nutritious diet declines because there is no replacement of new and nutritious plant tissue that can occur during the growing season.
The alternative to providing the pasture “all at once,” is to ration access gradually. More intensive winter grazing management, such as strip grazing, buffers the consumption of the most nutritious plants and plant parts, so that a more nutritious diet is available later into the winter. Once vegetation is stockpiled and “cured” at the end of the growing season, decline in nutritional value is relatively slow.
An opportunity for livestock to select a “better than average” diet can be preserved by using a rationing strategy. The greater opportunity livestock are given to select, the more nutritious a diet they can obtain. Managers control this through the total quantity of pasture which is accessible. In addition to extending the nutritional value of winter pasture, a rotational plan such as strip grazing can improve the utilization of the pasture through reductions in trampling and fouling.
A second capacity of ruminant livestock that can be exploited in winter grazing is their ability to recycle nitrogen. Dietary protein is essential for livestock, primarily to supply nitrogen. Optimal nitrogen concentrations in the rumen are necessary to maintain fiber digestion. Facilitating fiber digestion is critical to maintaining livestock performance on winter pasture because of the typically high fiber content of the diet. Research which has demonstrated adequate performance of beef cows when they receive supplemental protein every third day, or even once a week, demonstrates this capacity to recycle nitrogen and maintain adequate rumen concentrations.
Grazing managers can take advantage of the same phenomena. Since animal selection results in the highest-quality diet when access to “fresh” pasture is first provided, protein and therefore dietary nitrogen concentrations will be highest initially when a new strip is offered. Dietary quality may decline as the duration of occupation advances, but rumen nitrogen concentrations are likely to remain adequate. Providing a new strip every third day is probably sufficient to provide adequate nutrition for dry, pregnant mature beef cows.
Gerrish provided evidence from several ranches who were able to increase winter carrying capacity by 30 percent or more by implementing more intensive grazing management strategies than they had previously used. He also began his discussion with a reminder that grazing plans for winter need to be developed as part of a design for feed allocation for the entire year.
The South Dakota Grasslands Coalition continues to provide excellent opportunities for both new and established grazing managers to learn from outstanding speakers as well as from one another. If you haven’t attended one of their events, make the effort to get to the next one. If you’re not a member, consider joining – it’s a worthwhile organization!
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Outtagrass Cattle Co. cartoon by Jan Swan Wood for the Oct. 23, 2021, edition of Tri-State Livestock News