Herd Health
By Heather Smith Thomas
Windbreaks and Shelter for Fall-Calving Herds In climates where wind chill can be an issue during colder months, planning ahead for winter weather can save stockmen money (in reduced feed costs, reduced illness and health costs, and less loss of body condition—and better growth for young animals). When cattle are stressed by wind and cold, they seek shelter. If there are no natural windbreaks available, stockmen can provide artificial wind barriers to give protection from wind and drifting snow. Dr. Joseph Darrington, Ag Engineer, South Dakota State University, says shelter is important for fall-calving herds, depending on when they are calving. “This could be anywhere from September through November. The later the calving season goes, the more likely you might run into winter storms. There are two main types of windbreaks-- natural shelter such as trees or
to the windbreak and if there is snow with the wind it tends to dump a lot more of it right behind the windbreak.” This cuts down on the protected area for cattle to bed or stand behind the windbreak. It’s better to have a porous windbreak, so you don’t end up with a big snowdrift behind it, reducing the shelter area. “With 30% open and 70% solid you can expect the protected zone behind the windbreak to extend 10 to 15 and sometimes up to 20 times the height of the windbreak. The protected area is always estimated based on the height of a windbreak. An example would be a 10 foot tall fence slowing wind for about 100 to 150 feet behind it. If it’s a straight windbreak and the wind is coming head on, perpendicular to it, this creates a triangular protected zone behind it,” he says. Windbreaks are usually constructed to face prevail-
Constructed windbreaks should not be a solid barrier, rather have open spaces.
planted shelterbelts, and constructed windbreaks. One problem with a shelterbelt of trees is that they don’t have much foliage in winter/spring to stop the wind,” he says. “If you plant a shelterbelt windbreak, it’s best to have a couple rows of tall trees and a couple rows of smaller trees. If you need the windbreak in the fall, there is a lot of vegetation still under the trees during early storms and you may not need to include evergreens in your tree planting.” If you want more protection during winter and spring, it helps to have some evergreens because the other trees will have lost their leaves. Constructed windbreaks are generally made with boards (often placed vertically), leaving spaces between them rather than a solid barrier. “The target porosity, according to several studies, is from 20% porosity (open) and 80% solid, down to 65 or 70% solid. If you have more than 35% porosity (and 65% solid) or closer to 50-50, you lose some of the benefits of the windbreak; you’ll have more air velocity coming through rather than being pushed up and over,” explains Darrington. “The reason you don’t want a solid windbreak is because it significantly reduces wind speed right next 14 | November 2017
ing wind direction. If the wind tends to come from several directions some people create a curved/cornered windbreak. “In our region the predominant cold wind comes from the northwest, about 60 to 70% of the time. The best position for a windbreak here would be to run it from southeast to northwest, to be perpendicular to the prevailing wind. If ranchers want a larger protected area, they sometimes run another windbreak from northwest to southeast, creating an arrowhead shape pointing to north. This gives the greatest protection,” he explains. “When planting shelterbelts we situate them north-south and east-west. With constructed windbreaks or planted windbreaks they have their corner in the northwest.” Some ranchers also create shelters with roofs, especially for the baby calves to get into, so they can stay dry as well as out of the wind. “According to USDA studies, a young calf’s thermal-neutral zone (where it is comfortable and can do well) is about 50 to 68 degrees Fahrenheit. They can do fine below that temperature if they are out of the wind,” he says. After the newborn calf is dry and has nursed (gaining “fuel” to stay warm from the colostrum, which contains a higher level of fat and
TEXAS LONGHORN TRAILS
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