THE A - ZINC OF ZINC POISONING
by Carol Highfill
Zinc is extremely toxic to birds. Although a bird requires a certain amount of zinc to remain healthy, too much zinc is very dangerous and can cause degeneration in the liver, kidney and pancreas and even death.
Unfortunately, zinc is all around us, and given the opportunity, our "inquisitive" and "unceasingly exploring" charges will be attracted to some of these sources and can be poisoned. It only takes a small amount of zinc to endanger a bird's life. There ARE treatments available, so all may not be lost. However, their success depends upon the level of toxicity and how quickly they are begun.
So it is up to us as responsibile pet owners and breeders to learn more about this deadly metal and how to safeguard our birds. We need to know how to recognize the symptoms of zinc poisoning and what can be done if our bird becomes ill.
There are two types of zinc poisoning: acute and chronic. Acute toxicity is caused when a bird ingests a metallic object containing zinc or flakes of paint which contain zinc pigments. In this case a relatively large amount of zinc is ingested at one time and the levels of zinc in the body quickly become elevated.
Chronic toxicity usually occurs when small amounts of zinc are consistently consumed. Zinc is soluble in soft water and in acids. When galvanized dishes are used for water or for acidic foods (fruits and juices), the zinc can contaminate the food and be consumed. The amount of zinc ingested is less, but it is constantly being resupplied and causing internal damage to the bird's organs. Zinc rust from galvanized wire can be another cause of chronic poisoning.
Zinc is a cumulative poison, which is not easily eliminated from the body. Once ingested, it is deposited in the liver, kidneys, muscle and pancreas. There is limited excretion through the urine, intestinal tract and bile.
Prevention is the best method of dealing with zinc toxicity. Remove the sources of zinc and your bird will be safe and you will sleep better. Zinc comes from a wide variety of sources, but it must be ingested to cause harm. Since birds spend a majority of their time in their cages, this is the first area to protect.
Cages, Toys, Food and Water Dishes
Paint - Birds can injest flakes of paint. Today, most cage manufacturers use safe paints and powder coating, but do ask questions when buying a cage. If you have a cage with chipping paint, you should get the paint flakes tested for toxicity. If it is toxic, then either strip and repaint the cage or replace it. Be sure to use paints which are both lead and zinc free. Many anti-rust paints contain zinc, so check with someone knowledgable. If you don't want to bother, then replace the cage.
Galvanized Wire - Galvanized metal which has been electroplated is safe, but galvanized wire (hot dipped) is not. According to Avian Medicine: Principles and Application by Ritchie, Harrison and Harrison, birds can ingest zinc from cages and clips made of galvanized wire. Toxicity can be reduced (but NOT eliminated) by scrubbing the wire with a brush and vinegar or a mild acidic solution. This removes any loose pieces and the white rust (zinc oxide) which forms on the wire. Over time more white rust which is also poisonous will form, so enclosures must be re-treated periodically. You can read more about galvanizing in Dan Radovich's article "Galvanized Wire and Zinc".
Remember, that each bird is different. Some chew on their cages more than others and are thus more likely to ingest white rust. Bigger birds with more powerful beaks can break off pieces more easily than small birds. Most birds don't eat non-food items, but there are some who will. If you have birds in a large aviary with lots of branches or items to occupy them, they are much less likely to chew on the cage wire.
Hardware cloth is a very poorly made form of galvanized wire and should never be used. If you examine it closely you will see pools of lead and zinc metal in the corners of each square of the mesh - an invitation to a curious bird. Although a bit more expensive, if you must use galvanized wire, purchase galvanized after welded wire, which has less pooling and should flake less.
Food and Water Dishes - The zinc in galvanized bowls can be dissolved by water, fruit juices and acidic foods and contaminate them. Metal bowls should be made of stainless steel.
Toys - Quik Links, metal chains, eyelets and connections on toys are sometimes made of galvanized zinc metal. If the galvanizing process used was electroplating, then the zinc coating should not flake off and be swallowed. Electroplating binds the zinc into the underlying metal so that it will not separate. However if a piece of metal from a toy is bitten off and swallowed it can cause toxicity. Likewise if a metal piece of the toy falls into a soft food or water bowl, zinc can leech out into the contents and be consumed. Some toys and quick links are made of stainless steel. However, this is expensive and increases the cost of the toys. You should examine all toys you purchase for breakable metal parts (eg bell clappers) and buy the right size toy for your birds. And check the toys in the cage often. If you have a bird who likes to take toys in his beak and play with them, then be more careful about toys containing zinc.
Padlocks - There have been instances of zinc toxicity caused by padlocks. This has been reported in larger birds who are able to flake pieces of the coating off or to place parts of the lock in their beaks and dissolve some of the zinc.
Other Sources of Zinc
Ther are a number of other sources of zinc. They are only dangerous if they are swallowed or placed in a water or soft food dish which they can contaminate. Beware of items with finishes that flake off easily, which have small pieces which can be bitten off or are small enough to swallow whole. Common items which can contain zinc include:
Clips and Staples
Snaps, Zippers, Keys
Carpenter's Nails and Nuts
Costume jewelry or metal beads
Hanging window or shade pulls.
Pennies since 1982 (96% - 98% zinc)
Monopoly game pieces (98% zinc)
Common signs of zinc intoxication include excessive urine in the poop (polyuria), gastrointestinal problems, polydipsia, weight loss, weakness, anemia, cyanosis, hyperglycemia and seizures. Feather plucking has also been a reported symptom.
Acute toxicity cases demonstated lethargy, weight loss, greenish diarrhia, loss of balance (ataxia), recumbency and death. Chronic toxicity symptoms included intermittent lethargy, dysphagia and depression.
If you suspect your bird may have zinc poisioning, take him immediately to a veterinarian. He can perform a blood serum test which measures the level of zinc in the blood. Blood zinc levels of greater than 2 ppm (parts per million) are considered evidence of zinc toxicosis. For example, 1.63 ppm is considered an average normal level for cockatiels. The White Blood Count may also be elevated.
If your vet suspects zinc, he may take x-rays, looking for a piece of metal which may have been swallowed.
One method of treatment is the use of a chelating agent which binds with the zinc in the body and is then expelled. Injections of Calcium EDTA and D-penicillamine have been used. There is also an oral chelating agent, DMSA (dimercaptosuccinic acid).
If a piece of metal has been swallowed, then the primary treatment is removal either via catheter or forceps or by cathartics such as sodium sulfate, activated charcoal or mineral oil. Surgical removal can be used as well. Additional treatments are also available. Choice of treatment(s) should be made by a veterinarian based upon the individual situation