Dan Morrical, Extension Sheep Specialist, Iowa State University
Joseph Rook, Extension and Agriculture Experiment Station, Michigan State University
(Previously published with MSU College of Veterinary Medicine – Sheep publication: December 10, 2008)
- quantities of stalks are adequate
- weather conditions allow grazing
- fencing is available
- weathering causes minimal deterioration of quality
- you have enough sheep to fully utilize crop residue.
The major concern with introducing ewes to harvested corn fields is grain overload with rumen acidosis and overeating disease. Acidosis resulting from grain overload can be minimized by gradually introducing ewes to corn stalk fields. When ewes are initially turned into stalk fields they should have restricted daily access of one to two hours on stalks. Offering ewes a small amount (~0.5 lb.) of corn for three to seven days before grazing will also help to minimize problems with grain. Vaccination against enterotoxemia (“overeating disease”) with a subcutaneous injection of Clostridium perfringens type-D toxoid 4 to 6 weeks prior to entering stalk fields offers low cost added protection for the flock. If ewes have been boostered annually against enterotoxemia (overeating) before lambing, this management input can be skipped prior to going to stalks.
While there is limited sheep corn stalk grazing research data available if one extrapolates Iowa State University beef cow data it would appear that corn stalk residue can easily provide 150 to 300 ewe grazing days per acre. Grazing days per acre can be further increased if corn stalk fields are strip grazed in weekly to bi-monthly blocks. Strip grazing offers an additional advantage in that diet quality is elevated when sheep are released to new areas of the field on a timely basis. However, for most MI operations corn stalks present a challenge – in that inadequate ewe numbers are available to efficiently utilize residue when quality is best. Thus most MI producers will use only small areas for grazing (or graze sheep in combination with beef cows) to increase stocking rates and utilization.
Corn stalk grazing is an excellent way to feed the winter lambing ewe flock for six weeks or more in the late fall and early winter. If strip grazing is practiced, spring lambing flocks may be able to utilize stalks even longer. Corn stalks provide an abundant amount of dry matter for the ewe. However, one problem with stalk grazing is that it tends to be a feast-or-famine situation. Simply put, the quality of forage that the ewes initially select is very high. However, after a period of about thirty days the better, higher-quality plant residue has been consumed and the stalk is the primary feed resource left for grazing. Producers with large acres of corn stalks probably do not experience this phenomenon as available dry matter far exceeds the number of sheep grazing the acreage. Instead, over-consumption of corn occurs and ewes can become obese. However, both the feast or famine and the obesity situation can be corrected by restricting ewes to smaller areas (block or strip grazing). The area should be adequate to feed ewes for a period of one to two weeks, after which a new area should be made available to the flock. Block grazing can be easily accomplished with temporary electric fencing.
Harvested corn stalks contain adequate levels of calcium and phosphorous, so that a Ca:P mineral is probably not necessary. As always, ewes should have a selenium-fortified trace mineral salt or mineral available at all times. The most likely deficient nutrient in harvested stalks is protein. Under full feed, the need for protein supplementation is minimal and can be easily met with either one-half pound of legume hay every day or one pound every other day. If stalks are strip grazed (block grazed) or it is early in the season and stalk quality is high (the first thirty days after harvest), protein supplementation is usually unnecessary.
Corn stalks are an excellent feed resource in the field or a harvested forage, and producers serious about generating a profit from their flock or short of winter forage need to capitalize on this under-utilized feed resource.
How much feed is out there?
Forage availability can be determined from the approximate shelled corn yields of the fields that are to be grazed. Generally, available forage is expressed as ewe grazing days per acre (EGD/A). The following table can be used to estimate grazing days per acre for various body sized ewes. Please realize that these figures are just estimates that are dependent upon weather conditions, mud, and stalk deterioration.
|Corn Crop Yield in Bushel/Acre|
|100 Bushel/Acre||125 Bushel/Acre||150 Bushel/Acre|
|150 lbs.||622 EGD/A||778 EGD/A||933 EGD/A|
|175 lbs.||533 EGD/A||667 EGD/A||800 EGD/A|
|200 lbs.||467 EGD/A||583 EGD/A||700 EGD/A|
What can I afford to pay to graze neighbor’s corn stalks?
One standard method of leasing grazing on neighboring fields is to pay the owner on a per ewe per head per grazing day basis. A customary fee of $0.05/hd./ grazing day is often cited. Paying on a daily basis reduces risk to the flock owner. Open winter weather may prolong grazing and cost more, however, early snows may cause grazing to cease earlier – making up front per acre payments more risky. If a producer gets half as many ewe days as the values listed above (50% utilization is realistic), and is paying $0.05 cents per ewe per day, then the 100 bushel/Acre corn stalk fields would be worth about $15.00/Acre to a commercial flock with about 150 lb. ewes.
What’s the downside?
However, corn stalk grazing does come with a cost. There will be time and depreciation involved with building temporary electric fence. Water hauling may also be necessary. – However, the most important aspect of how well ewes perform on corn stalks is the amount of mud and weathering. Corn stalks lose quality very rapidly under wet, muddy conditions. Also remember that corn stalk quality is rapidly deteriorating when late lambing ewes are often being bred or in early pregnancy. Also remember that late season grazing of corn stalks may require some supplemental feeding of ½ to 1 lb. of good legume hay per head per day and/or even a little supplemental shelled corn. Also be alert to avoid the “feast or famine ” scenario that is often associated with the accumulation and melting of early season snows – especially during breeding and early pregnancy.