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Posted 23 April 2007. Forage and Grazinglands. Livestock Concerns with Salvaging Damaged Wheat Crops University of Illinois at Urbana-Champaign. www.aces.uiuc.edu Urbana-Champaign (April 13, 2007)--The Illinois Water Survey reports that the average last spring frost for southern Illinois occurs during the first two weeks of April. This year, that estimation has been correct. The recent cold weather is forcing producers to evaluate wheat stands for damage and consider possible salvage options.
"When evaluating salvage options, wheat producers should first consult with crop insurance adjusters to determine the extent of damage and requirements for making claims," advises Justin Sexten, University of Illinois Extension beef specialist. "Next, producers should read and follow all herbicide label restrictions for grazing and harvest of wheat. Herbicides used for wheat may not permit the mechanical harvest or grazing of wheat forage prior to maturity." After considering insurance and herbicide harvest restrictions, producers who want to harvest wheat by grazing or haying must now consider nitrate toxicity as a livestock-related problem associated with frost-damaged wheat. Sexten says nitrate is the most common form of nitrogen taken up by the plant, and nitrate toxicity occurs when the animal consumes more nitrate than the rumen microbes can utilize. The rumen microbes reduce nitrate to nitrite which is then converted to ammonia and used by the microbes as a protein source. When the animal consumes forages high in nitrates, excess nitrite is absorbed into the blood and converts hemoglobin into methemoglobin, which restricts the blood's ability to transport oxygen to cells. Animals suffering from nitrate toxicity will exhibit muscle tremors, incoordination and diarrhea. Blood will turn chocolate brown rather than the normal bright red. If symptoms are observed, contact your veterinarian, move the animals to an alternative forage source, and offer grain supplement to speed utilization of the excessive nitrate. Frost-damaged wheat will begin to decline in feed value as the damaged forage dies back; so, a timely harvest is important. Sexten says harvesting damaged forage as silage or balage is the best option since lower spring temperatures and short drying periods are not conducive to hay making. In addition, nitrates are stable in dry forages so stored hay will maintain the harvested nitrate level whereas ensiling the forage will reduce nitrate concentrations by 50 percent. While silage inoculates are not generally required for summer ensiling, cold weather has reduced the number of bacteria required for ensiling so forage experts are recommending silage inoculants. "If you are thinking about grazing wheat stands, remember that nitrates are concentrated in the lower portions of the plant. So, forcing cattle to graze lower stems and leaves increases nitrate toxicity risks," explains Sexten. "As damaged plants die back, animals may selectively graze the lower shoots, also increasing nitrate risks. If animals are grazed, provide alternative forage or grain sources to dilute dietary nitrate concentrations and improve ruminal nitrate utilization." Producers should test forages to determine nitrate levels. Make sure you collect a random sample of the forage being tested. Before taking samples, contact the feed analysis laboratory to find out preferred shipping methods and sample size. Acceptable nitrate levels in feed will vary with the class of livestock, stage of production, diet components, water source and feeding management. General recommendations are listed in Table 1. Table 1. Cattle Feeding Recommendations for Nitrate-Containing Forges
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