CAUTION! Fall Johnson Grass Grazing & Cutting

Precautions to Take Before Grazing and Cutting Johnson Grass Hay in the Fall

Johnson grass (Sorghum halepense) is a highly productive forage, often used for hay and grazing. However, it requires careful management in the fall due to potential toxicity risks that can endanger livestock. To ensure safety and maximize the forage value, here are essential precautions to follow before grazing or cutting Johnson grass hay in the fall.

1. Beware of Prussic Acid (Cyanide) Poisoning

Johnson grass contains compounds that can release prussic acid (hydrocyanic acid) under certain conditions. This toxin can be lethal to livestock, especially after events such as:

• First Frost or Freeze: Frost disrupts plant cells, releasing prussic acid.
• Drought or Stunted Growth: Stressed plants have higher concentrations of cyanogenic compounds.
• Regrowth After Frost: Young regrowth is particularly dangerous as it contains more prussic acid.

Precautions

• Wait 14 days after a frost or freeze before grazing or cutting the grass to allow the prussic acid to dissipate.
• Avoid grazing young regrowth following a frost. If cutting for hay, ensure it is mature enough to reduce toxicity risk.
• Test the forage for prussic acid levels if you suspect it might be unsafe for livestock consumption.

2. Check for Nitrate Accumulation

Johnson grass can accumulate dangerous nitrate levels, particularly during drought conditions or with excessive nitrogen fertilization. High nitrate levels can cause nitrate poisoning, leading to reduced oxygen flow in animals' bloodstreams.

Precautions

• Conduct a forage test for nitrates before grazing or feeding hay. Testing kits are available through local agricultural extensions or laboratories.
• Delay grazing or cutting until conditions improve if nitrate levels are elevated.
• If nitrate levels are high, ensiling the forage can reduce the concentration over time.

3. Mature the Grass Before Cutting for Hay

Cutting immature Johnson grass increases the risk of both prussic acid and nitrate toxicity. Additionally, the forage quality improves as the grass matures, making it safer and more nutritious for livestock.

Precautions

• Harvest Johnson grass hay at the boot to early heading stage to balance yield and nutritional quality.
• Allow hay to cure thoroughly. Proper drying reduces prussic acid content, making it safer for feeding.

4. Carefully Manage Grazing Patterns

If grazing Johnson grass in the fall, avoid excessive consumption of new or young growth to prevent toxicity risks.

Precautions

• Introduce livestock to Johnson grass gradually to prevent overeating.
• Provide livestock with access to alternative forages or hay so they do not rely entirely on Johnson grass.
• Rotate pastures to control grazing and allow time for regrowth to mature and reduce toxin levels.

5. Monitor Livestock for Signs of Poisoning

Even with proper precautions, it’s essential to monitor animals for signs of prussic acid or nitrate poisoning. Early intervention can save lives.

Signs of Prussic Acid Poisoning

• Rapid breathing or gasping
• Muscle tremors or convulsions
• Excessive salivation
• Bluish-colored gums
• Signs of Nitrate Poisoning
• Labored breathing
• Staggering or lack of coordination
• Blue or brown discoloration of mucous membranes
• Sudden death

If you observe any of these symptoms, remove livestock from the field immediately and contact a veterinarian for treatment.

6. Store Hay Properly to Maintain Quality

Proper storage ensures that hay remains safe and retains nutritional value for future feeding.

Precautions

• Store hay in a dry, well-ventilated area to prevent mold growth, which can further endanger livestock.
• Label bales if nitrate or prussic acid levels were a concern, so you can monitor how much is fed or dilute it with other forages.

Conclusion

While Johnson grass can provide excellent forage, managing it in the fall requires vigilance to avoid prussic acid and nitrate toxicity. Waiting for the right weather conditions, conducting forage tests, and monitoring livestock closely will ensure safe grazing and hay feeding. By following these precautions, you can make the most of Johnson grass while keeping your livestock healthy and productive throughout the fall season.