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Topics : Species and Forage Variety Trials : Species Fact Sheets : Sorghum & Sudangrass

Species: Sorghum & Sudangrass

Additional sorghum & sudangrass information via the Forage Information System (FIS)

Potential Animal Health Hazards Associated with Sorghum & Sudangrass

Prussic Acid Poisoning is a major concern when feeding sorghum, sudangrass, or sorghum- sudangrass hybrids. These species contain varying amounts of cyanogenic glucosides. In the rumen, these compounds are converted into prussic acid which is readily absorbed into the blood stream where it interferes with respiration. If prussic acid is present in the rumen and absorbed rapidly enough, the animal will soon die from respiratory paralysis.

Forage species and varieties may be selected that contain low levels of cyanogenic glucosides. Piper sudangrass has low levels and millet is free of these compounds. The management practices described below can also reduce the risk of prussic acid poisoning from sorghum, sudangrass, and sorghum- sudangrass hybrids:

  1. Graze or green chop only when they are greater than 18 inches tall.
  2. Don't graze plants during or immediately after a drought when growth has been reduced.
  3. Don't graze on nights when a frost is likely. High levels of the toxic compounds are produced within hours after a frost occurs.
  4. Don't graze after a killing frost until the plant is dry (the cyanogenic glucosides usually dissipate within several days).
  5. Don't graze after a non-killing frost until regrowth is greater than 18 inches.
  6. Delay feeding silage for 6 to 8 weeks after ensiling.

Nitrate Poisoning can be a problem under conditions of high nitrogen fertilization, heavy manure applications, drought, or overcast weather, when the plants can accumulate high levels of nitrates. When plants containing high levels of nitrates are eaten, the nitrates are converted into nitrites faster than they can be properly utilized by the animal. These excessive nitrites are absorbed into the bloodstream and alter the blood so that it can not carry oxygen. This causes rapid breathing, fast and weak heartbeat, muscle tremors, staggering and ultimately death if corrective steps are not taken.

The same precautions for prussic acid poisoning will help prevent nitrate poisoning. Millet can cause nitrate poisoning but not prussic acid poisoning. High nitrate levels will persist in forages cut for hay but will be reduced by one-half or so if the crop is ensiled. If you suspect high nitrates in the forage, have it tested by a forage testing laboratory.

Poisoning of Horses fed sorghum, sudangrass, or sorghum-sudangrass hybrids has also been reported. The exact cause of this poisoning is not known. Affected horses exhibit a staggering gait, urine dribbling, and aborting in pregnant mares. There is currently no treatment for this poisoning and affected horses rarely recover. Don't feed horses any of these summer-annual species.