Rory Lewandowski, OSU Extension Educator ANR, Wayne County
Brady Campbell, Program Coordinator, OSU Sheep Team
In our pasture
for profit grazing schools, it is often said that mechanical harvest of stored forages is about three times more expensive as compared to livestock harvest of forage in a managed grazing system. From this perspective, winter grazing offers an opportunity to improve the bottom line of pasture-based livestock production. The keys to making winter grazing successful depend upon planning ahead to make forage available for grazing, know the nutrient content of forages grazed as well as the nutrient requirements of the grazing animal, and some cooperation from Mother Nature along the way.
In general, winter grazing involves using either an annual crop or a stockpiled perennial forage. Annual crops commonly used for winter grazing include cool season species such as cereal grains or brassicas, as well as warm season annuals like corn. Mixtures of small grains or corn with legumes like forage peas, crimson clover, and vetch are used as well. In all cases the key is planning ahead. Depending upon the forage quality vs. quantity goals as well as the species, planting occurs at least 60 – 120 days or more before a killing frost.
In terms of forage quality, cereal grains (oats, triticale, wheat, barley, or rye) planted in early to mid-August and grazed in late October/early November will have crude protein (CP) levels in the low to mid-teens. If nitrogen was provided at planting, it is not unreasonable to expect CP levels of 16% – 18%. Energy levels as defined by total digestible nutrients (TDN) will be in the 58% – 60% range for early August plantings and 62% – 65% if planted in late August.
Additional forage types such as brassicas (turnips and radishes) are a high moisture, low fiber forage, with a very high digestibility, in the 80% – 90% range. The leaves often have a CP content of 20% – 25%, while the bulbs/roots contain 10% – 14% CP. Given these characteristics, brassicas act much like a concentrate rather than a forage. Adding fiber to the ration is recommended when brassicas are grazed. For this reason, a small grain/brassica mix works well. Some livestock producers have found that putting out some low quality, high fiber content hay when grazing pure stands of brassicas can also work well.
Perennial forages can be stockpiled for winter grazing by taking a last cutting, clipping, or grazing pass in early to mid-August and then let the pasture regrow and accumulate until the end of the growing season. Research has shown that this is the best compromise between quantity and quality of forage stockpiled. Beginning earlier can result in more tonnage, but quality will be lower; while beginning later will result in higher quality forage, but lower total tonnage. Tall fescue is our best stockpiling option, especially for late winter grazing, because it holds its forage quality value as compared to other grasses.
Nitrogen fertilization can increase both the quality and the quantity of the forage being stockpiled. Research results from multiple years of stockpiled fescue trials in southeastern Ohio show that applying nitrogen increases CP content of stockpiled fescue by an average of 2% – 3% as compared to the unfertilized fescue. Stockpiled fescue, especially if some nitrogen has been applied, could supply15% – 18% CP hay from late October to December and 11% – 15% CP forage from January to March. Research at the University of Arkansas evaluating forage quality of stockpiled fescue reported in 2006 indicated that TDN may be as high as 68% through November, declining through the winter months to an average of 58% – 60% TDN by February to March.
Now that we have an understanding of how these forages can be implemented into a grazing operation, we must then figure out how to utilize them. Grazing during the late fall and winter months can be challenging due to environmental conditions. In the case of sheep, we are lucky that our small ruminants have an added defense; wool. In the book titled “Effect of Environment on Nutrient Requirements of Domestic Animals” published in 1981, the authors provide data from previous research that supports that sheep are able to effectively withstand ambient temperatures as cold as -184ºF with roughly 4 inches of fleece. Although this is an extreme temperature, it demonstrates the value of wool that many of us take for granted. However, we must consider that this figure was derived from an ambient temperature reading without the effect of air movement or moisture. When accounting for these parameters in the form of wind and precipitation, this temperature threshold decreases significantly.
Think about how much wool your ewes have during the winter. Do you shear your ewes in preparation for lambing? For those that do, the same publication listed above supports that freshly shorn sheep (~0.3 inches of fleece), could withstand ambient temperatures of 5ºF. However, at this fleece length, when wet and exposed to air movement, their critical temperature increases significantly to 55ºF. It’s incredible how a little bit of rain, sleet, or snow can negatively affect sheep. Therefore, with this information in mind, it is crucial to remember that in these types of grazing situations, we must be cognizant of the conditions our ewes face.
In most cases, these winter forages are not directly located in our pastures. They may be in an adjacent field close to the barn or a field on the other side of the farm. Regardless of location, it is crucial that we provide some type of shelter and or wind break for our ewes that have short fleeces. For those with fleeces of longer length, shelter is also important as wool will become less effective from an insulation standpoint the more saturated or wet it becomes. Ensuring that we rotate paddocks quickly during wet and soggy events is important as well as this will reduce the amount of mud generated. When compared to cattle, sheep do not generate mud nearly as quickly, but mud can negatively affect the grazing efficiency of our sheep as it will require more energy to walk through the mud, wet and muddy legs require more energy to stay warm, and the potential issues associated with foot rot…
As we noted above, these forages will provide a lot high quality nutrition, but if we do not provide an appropriate environment for our ewes to graze in then our efforts will be lost. During this time period we must also consider that our ewes are in the first and second trimesters of pregnancy. This will increase their energy demands, which should be achieved by grazing these higher quality forages but could also result in disaster if our ewes are using a majority of their energy to generate heat and fulfill maintenance requirements. So, when considering how and when to feed these winter forages, remember to take both the plant and animal into consideration. Grazing too early could result in less total forage but may be more ideal from an environmental standpoint. Be sure to think all of scenarios before you begin to graze. Good luck and happy shepherding!