Portable Windbreak Fences

Using mobile windbreak fences for winter feeding on pastures and cropland

For portable windbreak fences to be effective, they must not blow over, even in extreme winds and they must be easy to move, so a producer never hesitates to move them on a regular basis.

Uses and Advantages of Portable Windbreaks

Livestock can be wintered away from the yardsite or corrals for part or all of the winter season.
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. This will reduce, or potentially eliminate the need for hauling and spreading manure with machinery.
Manure can be concentrated on areas where soil fertility is lacking, by placement of the windbreaks and feed.
Livestock can be fed on virtually any parcel of land you choose, provided there is good quality water or adequate snow available for a water source. Research has shown that mature cattle using snow as a water source perform equal to those drinking water.
The distance and amount of hay hauling may be reduced. Where windbreaks and livestock can be moved to parcels of land adjacent to fields where bales are made, the bales can be picked and fed as needed.
Fall and winter grazing practices such as stockpiling perennial forage, swath grazing, corn grazing, bale grazing, and crop residue grazing can be used on open parcels of land that do not have natural, or other manmade shelter.
Producers can winter livestock away from riparian areas. Manure packs in riparian areas, which often have natural shelter, can potentially contaminate water sources.
Livestock can be wintered on the same site for the entire winter season. In spring the portable windbreaks can be moved, allowing unhindered access for manure removal equipment without the risk of damage to windbreak fence.
Portable windbreaks can be sold separate from the land if a livestock operation is discontinued. Permanent windbreak fences are normally sold with the land and the selling price does not always reflect the cost of construction.
Portable windbreaks can be moved when snow accumulates, eliminating the need for snow removal.
On calving grounds, disease buildup can be reduced when the location of the site is moved on a regular basis.
Portable windbreaks can be moved to various pastures and used as temporary corrals for handling livestock.

Disadvantages of Portable Windbreaks

Requires regular moving to gain many of the advantages mentioned above.
Requires regular moving in pastures and hayfields to avoid killing the perennial forage with excessive buildup of residue and manure.
Requires regular moving on cropland so tillage equipment does not plug with leftover feed and straw.
Reduced manure hauling may be offset by the increased cost of hauling feed to the field. Most producers have the equipment to haul feed to the field, but usually have to hire contractors for manure hauling.
On parcels of land that have significant amounts of natural shelter, portable windbreaks will be less effective at controlling livestock distribution.
More expensive to build than permanent windbreak fence.
If not designed or built properly, will blow over in extreme winds.
If not designed or built properly, the bottom of the frame can freeze to the soil or become lodged in snow and bedding material, making movement difficult.

General Design and Requirements

The bottom of the windbreak should have approximately one foot of ground clearance to avoid snow from building up directly underneath.
The windbreak needs to be heavy and/or built with a broad base in order to counter the overturning force of the wind. With most pipe frame units, the width of the base should be at least 1.5 times the height of the fence.
As a general rule, one foot of fence protects enough area for one cow. A minimum of two units in a field is required so they can be placed at different angles to give protection from all wind directions.

Windbreak Porosity

The effectiveness of a windbreak is measured by the amount of wind reduction and the area in which the wind speed is reduced.
Optimum protection is obtained with a fence porosity of 25-33%. The protected area will extend eight to ten times the height of the fence. To get 25% porosity, space six-inch boards, two inches apart. To get 33% porosity, space six-inch boards three inches apart.
There is no significant difference in wind protection if the boards are mounted vertical or horizontal.
The force of wind, tending to overturn a windbreak, is made up of both pressure on the windward side, and suction on the leeward side. For that reason, a partially porous fence has to withstand the same amount of wind force as a solid fence. A force reduction from a reduced surface area is offset by increased suction when the wind penetrates the openings between slabs.

Vertical Wall Design

Most units are constructed using a vertical wall. This design maybe easier to construct, and may require less materials in the frame.
Slanted Wall Design give the option of blocking off the backside, so only younger stock have access to the area underneath the wall.
If used in summer for shade, the slanted wall can provide more shade.
Requires longer slabs to have the same effective height and may be more difficult to construct.

Mobility

An important feature for portable windbreak design is ease of movement with the available equipment. This applies to moving within a field, but may also apply to long distance moving. Ease of movement within a field becomes especially important when weather conditions are adverse. Ideally, the units should be designed so the operator does not have to leave the tractor seat. If movement cannot be done quickly and easily, the tendency is to leave the portable windbreaks in the same place for extended periods, cancelling some of the advantages. Units can be designed to lift and carry from the side, or tow from an end.

A. Side Lift

Requires a tractor with a front-end loader.
Can be lifted and placed end-to-end to form a long fence.
Less material is needed in the frame, because skids are eliminated.
Can be built with an elevated frame and legs, so only four corners touch the ground. This eliminates the possibility of the skids freezing in, or becoming lodged in snow and manure.
If snow accumulates on both sides, some snow removal may be required to gain access to a side.
When lifted from the side to be moved from one field to another, gates must be wider than the length of the portable windbreak, or lift must be higher than the fence.