Using Drought-stressed Corn for Silage
Expert offers tips for ensiling drought-stressed forage.
It is estimated that about 3% of the U.S. corn crop experienced drought conditions this year.1 If plants were stressed in the field, there will likely be challenges ensiling and feeding it, too.
“First off, nitrates can accumulate when corn is under drought stress, and high levels of nitrates can be harmful to animal health,” says Renato Schmidt, technical services–forage, Lallemand Animal Nutrition. “We can still produce good silage from drought-stressed corn as long as the crop is harvested correctly, ensiled well and carefully stored.”
Don’t take high-nitrate corn lightly, Schmidt warns. Even subclinical nitrate toxicity can result in decreased intakes, gains and production; decreased conception rates; embryonic death; and, occasionally, abortions.2
Nitrates accumulate in the bottom one-third of the plant. Therefore, producers should cut drought-stressed corn silage crops higher on the stalk.3 Assess the degree of drought stress in the field. Then, harvest based on one-half to two-thirds milk line and whole-plant dry matter (DM) of 32%-38% if ear and kernel development appear normal — at least 80% of normal bushel yields. If yield is severely reduced, then harvest based solely on whole-plant DM target value.
Next, drought-stressed corn tends to have low levels of lactic acid bacteria (LAB), which are essential to drive the initial fermentation process. These crops also tend to have higher levels of yeasts and molds and thus tend to have more aerobic stability issues.
A proven combination inoculant can help address both challenges. For example, the Biotal Buchneri 500 forage inoculant adds the LAB Pediococcus pentosaceus 12455 and Lactobacillus buchneri 40788 to help achieve a fast front-end fermentation and maintain aerobic stability throughout storage and feedout. In fact, L. buchneri 40788 applied at 400,000 colony forming units (CFU) per gram (g) of silage or 600,000 CFU per g of high-moisture corn (HMC), has been uniquely reviewed by the Food and Drug Administration (FDA) and allowed to claim improved aerobic stability.
The ensiling process itself can reduce nitrates by 50% to 70%. However, it’s important to give ensiling time to work.
“Never feed freshly chopped forage coming from a drought-stressed field,” he says. “It’s important to let forage ensile for at least three to four weeks. Then, introduce it gradually into the ration.”
Testing nitrate levels prior to feeding helps avoid toxicity. Silage can be incorporated at varying amounts depending on the results, but levels of 1.5% or greater should not be fed.
When harvesting drought-stressed forage, consider your own safety. Be cautious when unloading silage made from corn with high nitrate levels, Schmidt warns. “Nitrogen oxide gasses produced early during ensiling are lethal to both animals and humans.”
Schmidt notes these gasses are typically only a concern during the first few days of ensiling and tend to accumulate in low areas, as they are heavier than air. The gas can be colorless or look reddish-brown. To dissipate the gasses, run the blower 15-20 minutes before entering an upright silo, and use caution around vents in silo bags. Workers should wear a respirator, especially when entering an upright silo to guard against these gases and also prevent asphyxiation due to the carbon dioxide, the most common silage gas.
| Nitrate levels (%DM) and feeding recommendations | |||||
| 0-0.44 | ➠ | Safe to feed. | |||
| 0.45-0.88 | ➠ | Usually safe to feed with balanced diet. Limit to 50% of DM intake in pregnant animals. | |||
| 0.89-1.50 | ➠ | Limit to 20%-25% of DM intake. Use caution. Do not feed to pregnant animals. |
|||
| >1.50 | ➠ | Toxic! | |||
Editor’s Note: This article is provided by and reprinted with permission from Lallemand Animal Nutrition.
1The National Drought Mitigation Center. University of Nebraska-Lincoln. U.S. Corn Areas Experiencing Drought. June 27, 2017. Accessed July 13, 2017. Available at: https://www.drought.gov/drought/data-maps-tools/current-conditions.
2Townsend J. Animal considerations for nitrate toxicity when using whole plant corn as a feed. Purdue University School of Veterinary Medicine. Accessed July 13, 2017. Available at: https://www.extension.purdue.edu/dairy/articles/NitrateToxicityCorn.pdf.
3Kung, Jr. L. Management of Drought Stressed Corn for Silage. Cooperative Extension, Department of Animal & Food Sciences. University of Delaware.