You are here
Windbreaks Increase Cow Comfort While Lowering Energy Needs
Building a cowherd of 100 head has been Rusty Myskiw’s long-term goal. Hand in hand with growing the herd has come the need to provide plenty of winter shelter for the cattle.
Myskiw’s farm near Warren, Manitoba, sits on an open patch of prairie offering little protection from the region’s long, cold winters. It’s possible for blasting winds and subzero temperatures to send windchills plunging as low as -40°F. to -50°F.
“To be fair to the cattle, I need to provide protection for them,” he says.
By building permanent wood-slab windbreaks, Myskiw has done just that.
“Compared with the cost of putting up a bale windbreak of 300 straw bales like I used to do, building a permanent wooden windbreak of the same length will pay for itself in just a couple of years,” he explains.
Building costs aside, increasing the comfort of cows by shielding them from cold winds with any kind of shelter offers a potential savings in feed cost. Simply put, the colder a cow is, the more she eats.
Lorne Klein, Saskatchewan Agriculture regional forage specialist, explains why. “The lower critical temperature for a cow is minus -20°C. [-4°F.]. When the windchill drops lower than -20°C., she needs to consume extra energy to stay warm.”
Some sources put the lower critical temperature (LCT) of a cow much higher, in the range of 18°F. to 20°F. Sources indicating a -4°F. LCT limit this to cows in good condition. Thinner cows with poorly developed hair coats have a lower tolerance to cold, thus, a higher LCT.
For every temperature degree below a cow’s individual LCT, her need to intake energy increases by 1%.
a simple process for optimal protection
Sheltering cows from cold wind by building wood-slab windbreaks (pictured above) is a simple process. Typically, the windbreaks are made of 8-foot-long boards nailed vertically to two or three 16-foot-long, 2×6-inch horizontal stringers nailed to posts. The ¾-inch-thick boards are 6 inches or 8 inches wide.
Allowing space between the boards permits porosity, or airflow. “You want a little wind to flow through the fence so that you reduce turbulence on the downwind side,” Klein says. “The optimal protection is obtained with a fence porosity of 25% to 33%. This amount of porosity lowers wind speeds and also provides a large area of protection from the wind.”
By comparison, solid windbreaks do slow the wind to as low as 10% of its velocity, but only for a short distance from the fence. At a distance of just twice the fence height, wind speed has regained 25% of its velocity and increases sharply at a distance of four times the fence height.
With only slight differences between their effects, both 22% and 33% porosities slow wind velocity to less than 20% at a distance of four times the height of the fence. At a distance of 10 times the height of the fence, both porosities continue to lower wind velocity to 20% and 25% of its full force, with 33% porosity ensuring the lower wind speed at that distance.
“To get 25% porosity, space 6-inch boards 2 inches apart,” Klein explains. “To get 33% porosity, space 6-inch boards 3 inches apart. There is no significant difference in wind protection if the boards are mounted vertically or horizontally. Take the space at the bottom of the windbreak into account when figuring porosity.”
Aiming for optimal wind protection close up to the shelter, Myskiw settled on a narrow spacing of ¾ inch between the boards of his windbreaks after some years of experimentation.
“I still smoked when I built my first windbreaks, and I figured if I could light a smoke on the inside of the windbreak, that meant the cows would be comfortable,” he says. “My first windbreaks were solid with no spaces between the boards, but the wind swirled over the top of the fence and dumped the snow straight down.”
Over time, Myskiw built some 1,200 feet of windbreaks with a twofold purpose: providing both shelter and penning for various groups of cattle. Windbreak construction comprises all four sides of four pens measuring some 80 feet wide and 130 feet long.
Windbreaks also provide corralling and shelter in the main cow yard.
“On stormy nights, the cows can come up from their feeding ground and get out of the wind,” he says.
Using all pressure-treated materials, Myskiw builds windbreaks by driving 8-foot-long posts 6 inches in diameter 3½ feet into the ground. Posts are spaced 8 feet apart and support three 2×6-inch stringers to hold the boards.
To improve future windbreaks, he plans to run a slab horizontally across the top to stabilize boards and reduce the wear and tear they experience from the wind.
After the posts are in the ground, building the windbreaks is a family affair. “Everybody has a job,” Myskiw says. “The kids have a good eye for keeping the top of the fence straight. With four of us working, we can put up more than 60 feet of windbreak in an hour.”
create a stable solution
Portable windbreaks offer the advantage of flexibility. “The windbreak location and feeding site can be moved on a regular basis, so the nutrients from manure and urine are spread over a large area,” Klein says.
Whether buying pre-built portable windbreaks or building your own, he stresses the importance of having windbreaks that will not blow over.
“The stability of a portable windbreak is a function of the windbreak’s weight, height, and the width of its base,” Klein says. “As a rule of thumb, when an 8-foot-tall windbreak is built from oil pipe and wood slabs, the base needs to extend 7 feet on either side of the fence. It should be able to withstand winds of 60 to 70 mph without blowing over.”
Ease of movement ensures the most flexible use of the windbreak. Windbreaks built within a pipe frame permit lifting with a front-end loader on a tractor.
This design does not require skids and also permits the base to be comprised of an elevated frame and legs, so that only the four corners of the base are touching the ground.
“This eliminates the possibility of the skids freezing in or becoming lodged in snow and manure,” he says.
Windbreak design should allow 1 foot of clearance at the bottom.