Redroot Pigweed

Latin Name: Amaranthus retroflexus

Identifying Characteristics:

  • Oval to diamond shaped leaves
  • Prominent veins
  • Wavy leaf margins
  • Hairy stems
  • Produces flower spikes
  • Reddish taproot

Plant Longevity:

  • Annual

Where Commonly Found:

  • Tilled areas
  • Pastures
  • Hay fields
  • Roadsides
  • Waste areas

Time of Most Concern:

  • Midsummer

Compound that Causes Concern:

  • Unknown compound causes nephrosis (kidney disease)
  • Nitrates
  • Oxalates

Part of Plant Most Toxic:

  • Leaves
  • Stems
  • Roots

Livestock Species Affected:

  • Cattle
  • Goats
  • Sheep
  • Swine

Pasture, Stored Feed, Both:

  • Both

Clinical Signs:

  • Breathing with an open mouth
  • Difficulty breathing
  • Weakness
  • Sudden death

Amount Needed to be Consumed for Clinical Signs / Death:

The major toxic component of this plant remains unknown and studies concerning level of toxicity are not published. However, below is what we do know about the known toxic components in this plant.

  • Nitrate toxicity
    • Nitrate concentration varies from 0.04% to 2.9%, with green growth containing the least nitrate and wilted mature plants containing most
    • All parts of the plant contain similar amounts of nitrate
    • Toxicity typically observed when >1% nitrate in living tissue or when 5000 ppm nitrate measured in dry matter
  • Oxalate toxicity
    • Plants contain up to 30% oxalates by dry weight, with leaves having 3 times more oxalate as compared to stems
    • 0.1-0.12% of body weight oxalate can be lethal in sheep, if fed all at once; rumen flora can adapt over the course of 405 days to handle oxalate burden
    • About 3 lbs of plant with 30% oxalate can be lethal to sheep if fed all at once

Identifying Characteristics:

  • Oval to diamond shaped leaves
  • Prominent veins
  • Wavy leaf margins
  • Hairy stems
  • Produces flower spikes
  • Reddish taproot

Plant Longevity:

  • Annual

Where Commonly Found:

  • Tilled areas
  • Pastures
  • Hay fields
  • Roadsides
  • Waste areas

Time of Most Concern:

  • Midsummer

Compound that Causes Concern:

  • Unknown compound causes nephrosis (kidney disease)
  • Nitrates
  • Oxalates

Part of Plant Most Toxic:

  • Leaves
  • Stems
  • Roots

Livestock Species Affected:

  • Cattle
  • Goats
  • Sheep
  • Swine

Pasture, Stored Feed, Both:

  • Both

Clinical Signs:

  • Breathing with an open mouth
  • Difficulty breathing
  • Weakness
  • Sudden death

Amount Needed to be Consumed for Clinical Signs / Death:

The major toxic component of this plant remains unknown and studies concerning level of toxicity are not published. However, below is what we do know about the known toxic components in this plant.

  • Nitrate toxicity
    • Nitrate concentration varies from 0.04% to 2.9%, with green growth containing the least nitrate and wilted mature plants containing most
    • All parts of the plant contain similar amounts of nitrate
    • Toxicity typically observed when >1% nitrate in living tissue or when 5000 ppm nitrate measured in dry matter
  • Oxalate toxicity
    • Plants contain up to 30% oxalates by dry weight, with leaves having 3 times more oxalate as compared to stems
    • 0.1-0.12% of body weight oxalate can be lethal in sheep, if fed all at once; rumen flora can adapt over the course of 405 days to handle oxalate burden
    • About 3 lbs of plant with 30% oxalate can be lethal to sheep if fed all at once

https://bookstore.ksre.ksu.edu/pubs/s80.pdf

Beasely et al. Notes for Toxicology VB 320: A systems approach to veterinary toxicology. University of Illinois. 1994

Garcia et al. Amaranthus hybridus (syn. Quitensis) intoxication in cattle in Argentina: Case report. Toxicon. 2023

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