Livestock producers are starting to, or planning to, harvest drought-stressed corn, hoping to salvage it as livestock feed. University of Illinois beef extension specialist Travis Meteer answers some frequently asked questions:
Q: Do I need to test for nitrates?
A: Yes, elevated levels of nitrates have been well documented across the state. Cattle are valuable, and the test is inexpensive.
Q: When do I test for nitrates?
A: In most cases, before harvesting and after ensiling. Testing before harvest is a must if the drought-stressed corn will be grazed or green chopped. If the corn will be chopped for silage, test it after the ensiling process has finished, at least 3 to 4 weeks after ensiling. Do not feed it to livestock before knowing the test results.
Q: Where do I get a nitrate test?
A: There are labs in Illinois and surrounding states. ADM in Quincy, Ill., and Agri-King in Fulton, Ill., are certified with the National Forage Testing Association. A complete list is available at this link.
Q: What happens if I feed too much high-nitrate corn silage to my livestock?
A: They can get nitrate poisoning. Symptoms are blue-gray discoloration of skin, difficult rapid breathing, weakness, lack of coordination, rapid heartbeat with a subnormal temperature, and dark, chocolate-colored blood. Death occurs soon after the symptoms appear.
Q: Can I chop following a rain?
A: Wait 3 to 5 days. After rainfall, the increase in available moisture causes plant nitrate uptake to increase. The plant needs time to metabolize the nitrates. Some of the highest nitrate test results have come from samples that were taken after a rain. Be very cautious about chopping corn silage following a rain.
Q: What is the best way to harvest drought-stressed corn?
A: Chop for silage and ensile it.
Q: I have problems with uneven dry matter (DM) in my fields (hillsides are dryer than bottoms).
A: The moisture in the field may not be ideal for harvesting. Strongly consider using an inoculant to help mitigate risk.
Q: Is it beneficial to add inoculant this year?
A: Yes, the corn this year will likely be uneven, with DM hard to predict, and have low bacteria levels.
Q: Can I round-bale this drought-stressed corn?
A: Yes, but it will NOT reduce nitrate levels. Round-baling corn is challenging and puts considerable strain on equipment. Dry down of the stalk is crucial; the stalk dries better if crushed. Uneven moisture can result in bale spoilage. The stalk portion could be dangerous to the cattle. Many times the cattle will sort bales and leave the stalk last. If they are forced to eat the stalk and the stalk is high in nitrates, problems could follow. Make sure to test the bales for nitrates, preferably both before and after harvest.
Q: What about wet-baling drought-stressed corn?
A: Wet-baling corn is not a common practice. In theory, the material in the bales should ferment, decreasing nitrate levels by nearly 50 percent. A thicker plastic may be needed (6 ml) to prevent the corn from poking holes in the plastic and compromising the anaerobic environment.
Q: What is the feed value of drought-stressed corn silage?
A: Usually around 80 percent of the value of normal corn silage, ranging from 70 to 100 percent. The net energy of gain may be lower, but the net energy of maintenance is comparable. Protein will be higher, and the feed value is still good.
Q: What happens if the test results indicate high nitrate levels?
A: Hay, straw, corn silage with lower nitrate levels, and by-products can be used to dilute the feed so the nitrate levels are below the toxic level (>17,600 ppm nitrate). Consult with a nutritionist or extension specialist before feeding.
Q: I do not have a mix wagon. How do I dilute the corn silage with other feeds?
A: Limit-feed the corn silage and offer hay or another roughage free-choice. This is not a precise dilution method, but it will work. Make sure to have the silage tested to determine what portion of the total ration it can be.