Plants Causing Toxic Myopathies.

Plants Causing Toxic Myopathies involve certain toxic compounds found in specific plants that when ingested by horses lead to severe muscle damage and energy metabolism disruption.

Introduction to Toxic Myopathies from Plants

• Certain plants like boxelder, sycamore maple, white snakeroot, and rayless goldenrod contain toxic compounds harmful to horses.
• These plant toxins interfere with energy metabolism in muscle cells, leading to muscle damage.
• The condition primarily affects horses grazing on sparse fall pastures and can be fatal.

Toxic Compounds and their Effects

• Boxelder and Sycamore Maple:
• Contain hypoglycin A (HGA), a toxic amino acid.
• HGA is metabolized into methylenecyclopropylacetyl-CoA (MCPA-CoA).
• MCPA-CoA inhibits fatty acid β-oxidation, a crucial pathway for energy production in muscles.
• This inhibition leads to a condition called Seasonal Pasture Myopathy (SPM) or Atypical Myopathy (AM), characterized by severe muscle damage.
• White Snakeroot and Rayless Goldenrod:
• Contain benzofuran ketones (BFKs), a group of toxins whose exact identity and toxicity vary.
• BFKs inhibit cellular energy metabolism, although the specific mechanism may involve complex interactions among multiple toxic metabolites.

Clinical and Environmental Factors

• Horses grazing on sparse pastures, particularly in the fall, are at higher risk for these toxic myopathies.
• These myopathies present with rhabdomyolysis—breakdown of skeletal muscle—and cardiac myonecrosis—damage to heart muscle cells.
• The toxins are stable and remain active even when the plants are dried and used as hay.
• Additionally, toxins can be excreted in the milk, posing a risk to nursing foals.

Significance of the Research

• Understanding the plants and their toxins helps in diagnosing unexplained muscle diseases in horses.
• Awareness of how these toxins affect energy metabolism aids in prevention and treatment strategies.
• Knowledge that toxins persist in hay and milk informs management practices to reduce exposure risk.