Zinc is an essential trace metal that plays an important role in many biologic processes. Zinc toxicity has been seen in a wide range of animals. It is most common in pet dogs, possibly because of their indiscriminate eating habits and great availability of zinc-containing substances. Common sources of zinc include pennies, batteries, automotive parts, paints, zinc-oxide creams, herbal supplements, zippers, board-game pieces, screws and nuts on pet carriers, and the coating on galvanized metals such as pipes and cookware.
Zinc salts are formed in the stomach, absorbed from the small intestine, and quickly distributed to the liver, kidneys, prostate, muscles, bones, and pancreas. Zinc salts have direct irritant and corrosive effects on tissue and interfere with numerous metabolic processes, including the production and function of red blood cells. Diets containing high levels of zinc have caused longterm zinc toxicosis in livestock.
Signs vary based on the duration and degree of exposure. Signs progress from loss of appetite, vomiting, diarrhea, and lethargy to more advanced signs that include jaundice, shock, destruction of red blood cells, blood in the urine, heart rhythm abnormalities, and seizures. Lameness has been reported in foals. The liver, kidney, and pancreas can be damaged. X-rays of the gastrointestinal tract can reveal zinc-containing foreign bodies. Zinc levels can be measured in blood or other tissues, and changes in the blood and urine reflect the effects on various organ systems.
After stabilizing the animal with fluids, oxygen, and blood products as necessary, removal of the source of zinc as early as possible is critical. This often requires surgery or the minimally invasive surgical procedure using an endoscope. Inducing vomiting is usually not recommended.
Administering fluids to increase urine output is recommended to promote kidney excretion of zinc and prevent kidney damage.
If diagnosed and treated early, the outlook for animals with zinc poisoning is generally good. Eliminating sources of zinc from the environment is essential to prevent recurrence.