Summary
Oxalic acid is a strong organic dicarboxylic acid, and depending on the pH, oxalates exist as the acid, the acid ion, the oxalate ion (all soluble), or as salts with divalent cations. Oxalates play a role in plant metabolism and survival. Therefore, most plants contain oxalates, usually as a combination of more than one of these forms with a substantial portion as largely insoluble calcium oxalate crystals. Toxicity is determined by the concentration, chemical and physical form in the plant material, as well as feeding behavior and gastrointestinal morphology of the exposed animal. Some forms of calcium oxalate crystals can induce peracute skin/oropharyngeal trauma. The soluble forms, however, are responsible for most of the pathology after ingestion. In ruminants, the almost neutral, microorganism-rich rumen reduces significant absorption unless large doses of soluble oxalates are ingested, whereas in monogastric animals significant early absorption occurs during passage through the highly acidic stomach.