Know the nutrients and dangers that cornstalks contain
This year, one nitrate test on corn stalks isn’t enough for cattle producers. Nitrate levels can change dramatically from when a sample is taken and forages, such as cornstalks, sorghum-sudan grass, millet and fescue pastures, are harvested.
"Nitrate in the plant becomes nitrite in the rumen," says Tim Evans, University of Missouri veterinary toxicologist. "Nitrates absorbed into circulation from the ruman interact with hemoglobin in the blood, leading to methemoglobinemia, which reduces the ability of the blood to transport oxygen throughout the body of the animal."
The best prevention is accurate information, he says, adding that nitrate tests cost about $25. "Cows will most often eat the leafy areas of the stalks, which contain lower nitrate levels, but I don’t have a lot of faith in cows always eating what we expect them to," he says. "Testing is relatively easy to perform and inexpensive."
Symptoms of nitrate/nitrite intoxication include anxiety, lethargy, exercise intolerance, abortions in late gestations and death. Symptoms can appear as soon as one to four hours after eating, with abortions happening three to five days after consumption.
Test that Bale
Sampling cornstalk bales is similar sampling hay bales, but forage probes should be sized appropriately for corn stalks, says Justin Sexten, University of Missouri Extension beef specialist.
With the brittleness of stalks and husks, he advises cattle producers to use a larger probe, ½" to ¾" wide, and one that is very sharp to cut through the corn. To prevent stalks or husks from sliding off the probe, cut at slower speeds than for hay bales.
There are lots of nutrient variability in cornstalk bales, says Rick Rasby, University of Nebraska-Lincoln Extension beef specialist. "Of any residue, cornstalks have the greatest potential as feed for cow-calf operations."
"Test for moisture, protein and energy in the form of total digestible nutrients (TDN), and test for nitrates and alfatoxins. Normally, nitrates not a major concern, but in extreme drought years, its best to test," Rasby says.
With high feed costs, farmers may think about grinding corn stalks to utilize the whole plant. "At that point, you’re not going to let cows select," Rasby says. "The smaller the screen you grind through, the less that the cows will sort—I suggest a 3" to 5" screen. When you are feeding the entire residue, a nutrient analysis as well as a nitrate test is really important."
Watch an video form University of Nebraska-Lincoln Extension featuring Rick Rasby, explaining how to sample corn stalk bales: