K Mortensen wrote: I guess if chickens decide to take a mouthful here or there they will probably be ok? I saw one source that says cows can eat it.
In both those cases, it's a matter of dosage. Picky browsers like chickens (or goats) are not going to get a big dose of oxalate in the
course of their usual eating habits. Plus ruminants may have some added defenses that we do not have to break down oxalate. Oxalate is what gives sorrel its tangyness and also why rhubarb leaves are considered "toxic".
It's toxic in large doses, as it builds up and creates kidney stones, which is different from the toxicity of Digitalis or nightshade, which will make you fall over dead quickly.