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       Wednesday, July 23, 2014

February 2009

Portable windbreak fencing for livestock shelter is an old idea that is gaining in popularity.   In recent years, there has been a renewed interest in constructing and using mobile windbreak fences for winter feeding on pastures and cropland.

Two of the most important features for portable windbreaks are:

  • They do not blow over, even in extreme winds.
  • They must be easy to move, so a producer never hesitates to move them on a regular basis. Ideally, the operator should not have to leave the tractor to move a windbreak.

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 water or adequate snow available for a water source.  Research has shown cattle using snow as a water source perform equal to cattle 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 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.
  • Feeding location can be away from the portable windbreak, and moved on a regular basis to avoid buildup of residue near the windbreak.    

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

  • Portable windbreaks need to be ruggedly built to withstand the stresses of moving and wind action. 
  • The bottom of the slab fence should have about 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.
  • Maybe easier to construct, and may require less materials in the frame.

Slanted Wall Design

  • Has 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.
  • May be more difficult to construct.

Mobility

An important feature for portable windbreak design is ease of movement with the power equipment available.  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, canceling 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.

B.      End Tow

  • Does not require a tractor with a front-end loader.
  • Requires more material in the frame for skids.
  • Skids may freeze to the soil, or become lodged in snow or manure.
  • Can be moved through narrow gates.
  • May not be as maneuverable, or versatile as side lift fences.

C.      Long Distance Moving

  • Can load on a flatbed trailer.
  • Can design with temporary, or permanent hitches and wheels.

Portable windbreak fence design samples:

This design requires the least amount of steel tubing in the frame. The horizontal wooden planks are not fastened to the frame, but are held in place when the slabs are nailed to the planks. The base is elevated with only four points touching the ground, reducing the possibility of freezing in. The base needs to be wider to prevent overturning in high winds.

Steel tubing at top of slab fence. Bottom of slabs should have one foot of ground clearance to avoid snow buildup on base.

Steel tubing at top of fence for inserting the tines on a bucket of a front end loader with a grapple fork.

Eight foot wing extension on a hinge at the end of the windbreak for opening and tying to the next portable windbreak.

This unit has three sections permanently hinged together.

This unit uses angle iron on the support legs.

Slanted wall design. Railing on back so young animals can be bedded underneath. Cross braces are welded eighteen inches high so they do not become embedded in manure pack.

Sturdy unit that requires relatively more steel tubing. Base has a significant amount of contact with the soil surface, increasing the risk of freezing in. Bottom of slabs should be elevated one foot.

Discer frames salvaged and bolted together for bottom fence support.

Slanted wall design using salvaged power poles with permanent back axle.

Model made from salvaged harrow hitch. Can be opened for field use and folded for transport.

Unit with temporary hitch and wheels added, for long distance moving. Extensions are inserted into the pipe stubs at the base for greater base width when the unit is set down.

Unit with 3 horizontal planks and 15 foot wide base to prevent overturning during high winds. Slight angle on legs could be increased so only tip of pipe touches ground. A higher angle prevents both freezing in of the base and skating during high winds. Bracing farther out on the legs may be needed.

Very sturdy unit requiring alot of steel pipe and labour.

Portable Windbreak Fences - Plans and Drawings

 

Plan for portable windbreak fence

Most effective protection is achieved with fences of 25 to 33 per cent porosity. Effectiveness extends for 8 to 10 times the fence height to leeward.

  1. slatted fence, 25 to 30 per cent porous
  2. 2 x 6 rough rails at 24" to 32"
  3. 6" pipe skids, sand fill for ballast
  4. sway bracing every 24 feet
  5. sub-frame of steel pipe
  6. 4" steel pipe main post
  7. adequate clearance, 12" to 16" typical

Digestible Energy Requirements
(Source:  Dr. Dave Christensen, University of Saskatchewan)

Will beef cows require more energy in their feed if they are wintered without bedding on open fields using portable windbreaks for wind protection?

The value of soft field snow as bedding is uncertain and needs to be studied.  Producers have observed that cows will readily bed in snow that is relatively soft.  Cows will avoid bedding on the same spot twice, where the snow has turned into an ice pack.

The following table compares digestible energy requirements (Mcal/day) of a 1,300 lb large frame cow at mid-pregnancy using three wintering options.  The average wind speed in Saskatchewan during December is 17.3 km/hr.  Average wind speed behind a portable windbreak is estimated at five km/hr.  Most of the information on effect of temperature on cattle is from feedlot or cold chamber studies.  Therefore, the values may not be accurate for cows bedding on soft snow.  The digestible energy requirements are based on estimates rather than direct observations.

 

Windbreak Fence

Windbreak Fence

No Windbreak Fence

Bedding

No Bedding

No Bedding

0 degrees C

20.7

26.1

31.6

 

 

 

 

-30 degrees C

26.9

32.3

37.8

 

References

  • Saskatchewan Agriculture.  Porous Windbreak Fencing, Plan S-104.  March 1993.
  • Manitoba Agriculture, Food and Rural Initiatives.  Portable Wind Fences: Good Tools for Management Intensive Grazing. 1996.

Acknowledgments

This publication was written by Lorne Klein, Saskatchewan Agriculture.
Dennis Darby, Alberta Agriculture Engineering Services assisted with comments and provided the drawings.

Thank you to the following producers and businesses for providing pictures and information:

  • Merle Heibert, Donavon, Saskatchewan
  • Ranchers Welding Ltd.,  Cromer, Manitoba
  • Paysen Livestock Equipment Inc.,  Central Butte, Saskatchewan
  • Olds College,  Olds, Alberta
  • R&H Feeds, Kelliher, Saskatchewan
  • T4 Ranches, Carnduff, Saskatchewan
  • K2 Elk Company, Weyburn, Saskatchewan
  • Paul Cameron and Bob Bennet, Arcola, Saskatchewan
  • EUR Ranches Ltd, Lake Francis, Manitoba
  • Roger Meyer, Minton, Saskatchewan
  • Don Gilford, Clearwater, Manitoba
  • Ross Hillrud, Ceylon, Saskatchewan
  • Miles McNeil, Alameda, Saskatchewan
  • Marvin Hoffman, Grenfell, Saskatchewan
  • Schindel Ironworks, Radville, Saskatchewan
  • Chad MacPherson, Moose Jaw River Watershed Stewards Inc.

 



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