Managing Forages After a Frost
With a strong likelihood of a frost setting over the Midwest this weekend, our phone lines have been lighting up with questions regarding how to manage forages after a frost. The main concern particularly lies with products in the sorghum family. We’re hoping this guide help calm and simplify the three main concerns regarding these forages.
What are the three main concerns?
- Prussic Acid Poisoning
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Prussic acid is found in plants from the sorghum family and is hydrocyanic acid, a compound that can ultimately lead to death by asphyxiation. Symptoms can include difficulty breathing, excess salivation, and even convulsions.
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Ruminants are most susceptible to prussic acid poisoning
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It’s more concentrated in young plant tissue, in parts less than 18” tall
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- Nitrate Poisoning
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Nitrates are a concern specifically with grasses.
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As the growing season gets cooler, plant development slows, resulting in higher concentrations of nitrates. High nitrate concentrations in rations can result in the lack of usable oxygen within the animal. This can lead to reproductive problems and issues with muscle tremors and scours.
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Nitrate levels will be more concentrated within the lower parts of the stalks.
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- Bloat
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Bloat is a concern directly related to feeding legume species. Bloat concerns should be elevated when feeding legumes one to two days following a hard frost or freeze.
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What Should I Do About This?
- Managing Prussic Acid
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Wait to graze or harvest 5-7 days following a hard frost and 14 days following a non-killing frost.
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If you see new growth after a non-killing frost, wait for a killing freeze and then delay grazing for harvest for 10-14 days.
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If mowing for hay or silage, you can mow any time after a killing frost. The cyanide compound will dissipate as the forage is drying and won’t be a concern to cattle.
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- Managing Nitrates
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Since nitrates are more concentrated in lower parts of the stalk, raising your cutting height or not letting the forage become overgrazed is the best practice.
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- Managing Bloat
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Bloat is rarely a concern as there’s usually other grasses in an animal’s diet that will dilute the levels of legume in the ration.
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If there’s still concern, try to move animals to a grass-based diet for two days after a hard frost.
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We are hoping this crash course on managing forages after a frost or freeze can help you sleep a little easier at night. If you’ve got any further questions, feel free to reach out to our experienced and knowledgeable agronomists at Elk Mound Seed at 715-879-5556.
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