Corn crop residue is practical for feeding dry, gestating beef cows in mid gestation providing they have average or better body condition. Managed correctly, one acre of corn residue can yield up to 60 animal unit grazing days (60 days of grazing for a 1000 pound animal).
Grazing "efficiency" will determine exactly how much feed is realized from corn residue. Moveable electric fencing can increase utilization up to 50% by allowing cattlemen to control the amount of area grazed thus, preventing the cattle from "selective" grazing or "trampling" many of the leaves or husks. "Strip" grazing the cows will also reduce the potential for acidosis in situations were there may have been excessive field losses of grain. Simply "dumping" the cows onto the entire corn field will be least efficient but will allow more residue to remain on the field over the winter for cover. Cattle will select and eat the grain first, then the husk and leaves, and finally the cobs and stalks.
Fields containing corn residues should be grazed soon after harvest for optimum quality, and fields with poor drainage or compaction problems should not be grazed for extended periods of time. Producers with a conservation plan should check with NRCS to be certain that the grazing of corn stalks does not violate the plan.
If corn stalk fields are not presently fenced, temporary electric fencing is an economical alternative. Harvested corn fields can be encircled with a single strand of poly or high tensile wire supported with fiberglass posts for less than $10 per acre. Even if a fence charger must be purchased to allow the grazing of corn residue, up to 45 days per acre of feed may be provided a typical Ohio brood cow at a cost of under 25 cents/head per day. And, of course, the materials purchased to provide this temporary boundary may be reused from year to year, thus, making the "annual" cost of ownership even less.
While corn residue offers a considerable amount of digestible energy and fiber, it's always good to review the palatability and practicality of utilizing crop residues which result from either corn or soybean harvest as a significant feed source, especially if they must be mechanically harvested and transported for feeding.
Of the two, certainly soybean stubble bales must be viewed as a last resort unless you have a bale processor and feed it in limited quantities to "dilute" other high quality feeds in the ration. In fact, if your vision for utilizing soybean residue is simply placing bales of the "feed" in bale feeders, it's probably not worth the time, fuel, wear on the machinery, and effort it takes to gather it. While it can have 35-40% TDN and nearly 4% protein, this is less than even wheat straw (review the article linked here by Steve Boyles on feeding straw). Simply put, as soybeans increase in maturity they increase in lignin and lignin is not digested well in the rumen. Soybean stubble might make marginal bedding, but twigs gathered from trees in your yard might make comparable feed.
While corn residue has much more merit than soybean residue as a feed source and may be viewed as comparable to average grass hay, palatability of the stalks can be a problem. The husks and kernels of corn that fall during the process of harvest are the most palatable, and will be readily consumed. This lends itself very nicely to grazing being by far the best method of harvesting corn residue, whereas, baling residue will likely cause loss of the kernels.
When it comes to baling and transporting corn residue - and especially if you're thinking about traveling very far with it - consumption versus waste becomes a consideration worth pondering. The husk, leaf, and any kernels in the bales, which will likely be a small percentage of each bale, will be readily consumed if fed in a bale ring. If you have a bale processor, much of the stalk may be consumed also. However, if you're simply placing corn residue bales in bale rings, the abundance of corn stalks which will remain after the more desirable parts of the bale are consumed will likely become bedding. If you must feed baled corn residue in this fashion, consider simply pushing the chopper or spreader on the back of the combine forward and dropping the residue that comes through the thresher in a "windrow" and then bale only these windrows. The resulting bales will be a much higher percentage of the palatable portions of the corn residue.
As you consider baling and transporting baled corn residue to your cows, carefully consider the harvest and transportation costs involved on a "per consumable and digestible ton of dry matter" basis. Don't forget about storage and feeding losses. In addition, according to past OSU Extension fertility specialist Robert Mullen, when you remove a ton of corn crop residue from a field you're taking with it 6 pounds of P2O5 and 25 pounds of K2O which must be replaced or redistributed to the field.
Corn stover also contains organic matter that when returned to the soil does have value, but it is difficult to put a dollar value on it. Continued removal a significant portion of corn crop residue may have negative repercussions in the long-run in the form of decreased soil organic matter, especially if some organic matter, perhaps in the form of manure, is not returned to the soil.
Grazing corn crop residue may prove valuable and soil friendly. However, carefully consider the pros and cons of mechanically harvesting and moving residue to the cow herd. In the mean time, see the OSU Extension Fact Sheet "Grazing Corn Residue" found at: http://ohioline.osu.edu/anr-fact/0010.html for more detail.