Earlier in my life, I lived on the Iowa-Minnesota-Dakota border. Up there, snow is part of the economy, and we would get aggressive about dealing with it. Here in Missouri, people tell me, “God put the snow here, and he will get rid of it, too.” But coming from the North, I know that God is OK with snow in June. That snow needs to go.
When it comes to managing cattle in the winter, one way to reduce cold stress is to ensure they have a windbreak or shelter belt. This provides both protection and snow management. Mitigating the effects of wind chill helps reduce feed needs, illness, stress and health costs. We also see better gains in calves and improved body condition in cows. Windbreaks are particularly helpful to calving and young animals.
Natural shelter belts may have trees that don’t have much foliage in the winter and early spring to stop wind. If you plant a shelter belt, use two rows of tall trees and two rows of smaller trees. For the most protection, include conifers. (I am channeling my inner Norskie.)
If building a windbreak with boards, use vertical 2x4s with a 0.75-inch to 1-inch gap between them for an 80-percent solid structure. You can also use rigid rib steel sheets that are 30 inches wide. These are wide enough for calves to hide behind. When placed 36 inches on center, they have adequate gap, and they go up fast. Windbreaks made with slabs are cheap and work well for this application.
If the windbreak is less than 65-percent solid, then you start to lose the sheltering effect. There’s more air coming through rather than being pushed up and over. You want to create a dead zone for the air to protect the cattle. A stream is a good example. If there is a rock in the stream, the water goes around the rock. Right behind the rock, there is an “eddy,” an area where there is still water. This is how you get turned around in your canoe on a river. You nose the craft around the rock, put it into the eddy and the current pushes the stern faster, turning you around.
A solid windbreak is not the first choice, either. It reduces wind speed right next to the windbreak, and snow will dump against it. This reduces the protected area for cattle to bed or stand behind. It is better to have a porous windbreak that is 70 to 80 percent solid. The protected zone behind a windbreak extends 10 to 20 times its height. For example, a 10-foot-tall fence slows the wind for about 100 to 150 feet behind it. If it is a straight windbreak, and the wind is coming head on, this creates a triangular protected zone.
It’s a double whammy if cattle get wet. Their critical temperature is higher, and wind magnifies the cold stress. A dry winter hair coat is good insulation against the cold. When the hair is standing up, fluffy with air spaces between the hairs, the insulation effect is substantial. However, wet hair is flat and changes the cow’s thermal neutral zone. Wet winter hair has the same insulation capacity as summer hair. That is, cattle will get cold at 60 degrees when wet.
Some of the coldest days for cattle are when the temperature may be higher but it’s wet. In the Atlas storm of October 2013 in the Dakotas, a substantial number of cattle died. The reason for the mortality was that it rained first and then got cold. The cattle had wet hides and were unable to stay warm. It didn’t get really cold, just cold enough they couldn’t maintain body heat without that insulation. They were chilled too much for too long.
Bottom line, if you can keep cattle dry and out of the wind during the winter, it will improve their health and well-being. Windbreaks can be part of the solution.