By Mark Parker
The scramble to find forage for cattle in drought-stricken areas has producers taking a hard look at corn stalks.
Like his counterparts in other parched portions of the territory, Labette County, Kansas, Extension ag agent Keith Martin has been covered up with questions about utilizing corn stalks as forage.
“Corn stalks represent a real opportunity for cattlemen who are in need of forage,” he said, “but we need to keep several considerations in mind. If you’re baling stalks you have to be able to cover your baling costs as well as the value of the nutrients you’re removing from the field.
"If you’re buying baled stalks you have to assess their value compared to that of hay," Martin said. "And if you’re feeding stalks - either baled or standing - I’d advise you to get a forage test so you know the nutritional value of what you’re feeding as well as a nitrate test to determine the potential for toxicity problems.”
Kansas State University Research and Extension Area Beef Specialist Karl Harborth seconded Martin’s advice on forage testing.
“Test what you’ve got - it’ll save you money because you’ll know how you need to supplement cattle consuming stalks,” he said. “Generally, you’re going to need to supplement a source of protein, possibly an energy supplement and provide a good trace mineral mix that includes vitamin A. You can get general estimates on the quality of stalks but it can be highly variable so a forage test is a pretty inexpensive way to keep from either over-supplementing or under-supplementing your cattle.”
Kansas State University rates early-grazed corn stover in the ballpark of 6.5 percent crude protein and 52 percent TDN. Those figures drop to 3.5 percent crude protein and 44 percent TDN later in the grazing season and baled stover is estimated at 5.2 percent protein and 49 percent TDN.
Utilization, of course, is much different for baled versus grazed corn stalks. Shredding, raking and baling harvests approximately 80 percent of the stover, according to Iowa State University, compared with 65 percent for raking and baling and only about 25 percent for grazing.
Harborth pointed out that baled stalks can work well in a limited feed situation where there is no grass available. If possible, he added, grinding the bales to reduce particle size will significantly increase utilization.
For cattle grazing stalks, he suggested a couple of things to keep in mind. First, the nutrient value of the stalks will go down with time. Cows will select the higher quality grain and leaves first, leaving the low-quality stalks until later.
Strip grazing, Harborth said, might help moderate that situation but in all circumstances, it’s important to keep a close watch on cattle condition.
He also suggested that producers turn their cows out on stalks for the first time on a full stomach.
“Don’t put them in hungry,” he said. “There may be potentially high nitrate weeds such as pigweed present and those cows are going to go first to something that’s still green.”
Regarding nitrate potential, Harborth urged producers to test both hay and standing stalks for toxicity. He pointed out that there is a new product on the market called BovaPro, which moderates the potential for nitrate toxicity problems but emphasized that it isn’t a substitute for good feeding management.
BovaPro, which comes in bolus form, costs about $8 per head and one treatment is supposed to last for about 180 days.
In Labette County, Martin has been testing a lot of stalks. The quick field test that he uses determines only the presence of nitrates and not the concentration. Still, he said he has found the presence of nitrate in pretty much everything he’s sampled.
“Nitrates are more concentrated in the lower part of the plant and much less so in the leaves,” he said. “If you’re grazing stalks the cattle are going to eat those leaves first and you may be OK but there is still no substitute for testing - it’s pretty cheap insurance.”
Martin also urged producers who are baling stalks - either for sale or for their own use - to keep their real costs in mind. In addition to fuel and some extra wear and tear on equipment, harvesting stalks in bale form does remove some nutrients from the soil, which would otherwise help feed next year’s crop.
Using data from a University of Minnesota Study and current fertilizer prices, a pound of corn stover residue contains about 32 cents worth of nitrogen, and 21 cents each of phosphate and potash. They estimate 15 pounds of nitrogen ($4.80) in a ton of stover with 5.9 pounds per ton ($1.24) of phosphate and 25 pounds per ton of potash ($5.25).
The final value depends on the amount of residue present and the amount that is actually taken off either by baling or grazing. The Minnesota information suggests that you can get a rough estimate by multiplying yield per acre times 56 pounds and adjusting that figure according to the percent you expect to actually utilize.
One Iowa State study estimated that harvest of corn residue at a height of 16 inches removed approximately $23 worth of nutrients per acre but, again, the amount varies significantly according to the amount of residue present.
In a grazing scenario, Martin said that there would likely be little or no loss of nutrients since they would be recycled by the cattle back to the soil.
In that grazing situation, he added that cattlemen can expect to get roughly 45-60 cow days per acre and suggested that grazing stalks would probably be best suited to dry cows rather than lactating cows.
Martin noted that a lot of drought-stressed soybean acres are also being harvested for hay. Soybeans can be a relatively high quality forage but that is highly variable according to the condition of the crop at baling.
Mark Parker writes for Farm Talk in Parsons, Kan.