Onions (
Allium spp) are toxic to poultry. If they are ingested in large enough quantities (more than 0.5% of the bird's body weight), onions can damage red blood cells and cause heinz body anemia.
All forms of onion are potentially toxic--dehydrated, cooked, powder, raw and includes garlic, leeks, shallots, and other plants of the
Allium family.