Toxins that Effect Backyard Chickens

A POISON by any other name is still a poison. To paraphrase Paracelsus from 400 years ago, it’s ‘the dose that makes the poison’. Simply stated, almost anything in an overdose or a diet restricted to only one ingredient would eventually become toxic to your birds. A misplaced decimal point in medication dosage can cause toxicity, and I’ve already written about the toxicity of a group of drugs used to treat coccidiosis called sulfonamides. Water mixable medications can become toxic if the weather is hot and the birds are drinking more water than normal. Even high levels of certain vitamins, such as A and D, can be toxic and some doses of medication that are perfectly fine for chickens and turkeys can kill your waterfowl. (Remember that waterfowl generally consume four times the water that chickens do.)

Toxins (or poison), fall into several different categories. I can’t list them all here, but I’ll try to give you an overview for general reference.

Again, the use of sulfonamides for the treatment of coccidiosis is highly discouraged. Especially with the availability of amprolium, which is safe. An effective dose of a sulfonamide is toxic to poultry, and can have a negative effect on the immune system. Hemorrhagic syndrome and organ damage can occur as a result of sulfa poisoning, particularly in the liver and kidneys. I discourage the use of sulfonamides for all poultry, including waterfowl, unless amprolium is unavailable. In this case, use a ‘safer’ sulfa such as sulfadimethoxine or sulfamethazine. Avoid Sulfaquinoxaline (SQ).

Some antibiotics can be troublesome if their use is not controlled. In turkey poults, the subcutaneous injection of Gentamicin can cause depression, edema, injection site hemorrhage, and kidney damage. Streptomycin (and dihydrostreptomycin sulfate), injected intramuscularly (IM), can cause respiratory distress, paralysis, and mild convulsions. Baytril is one of the safest and most effective broad-spectrum antibiotics available.

Some antiprotozoals such as Nitrazol and Emtryl have caused growth depression, drop in egg production, incoordination and tremors, convulsions, and death in geese, ducks, pigeons, and turkeys. Doses safe for other poultry may be poisonous to waterfowl. Quinacrine HCI (Atabrine), is fatal at a dose of 50mg/kg of body weight in pigeons, but is safe for other poultry at that dose.

Parasitic and worming treatments should also be used with caution. When you worm your birds, you’re giving them poison to kill the worms. With that in mind, you should never worm a sick bird as a shotgun approach to treatment. Rule everything else out first. Benzimidazoles (cambendazole, mebendazole, and fenbendazole), and phenothiazine are all pretty well tolerated by most birds. Ivermectin is probably the safest though.

Levamisole (and tetramisole, which is no longer available in most countries), should be used with caution. (Because of it’s chemical makeup, an effective dose of levamisole is half that of tetramisole.) It has a wide range of toxicity from as little as 66 mg/kg of body weight in wild birds, on up to 300 mg/kg in geese. Levamisole can be toxic to ducks at 40-80mg/kg of body weight.

Under the group of minerals and metals, three stand out as the most problematic: sodium chloride or sodium bicarbonate (salt), lead, and calcium (as in the over-use of oyster shell).

Most sodium problems arise as a result of young chicks and turkey poults consuming too much saline water. Avoid using softened tap water to supply water to your birds while brooding. Some waterfowl have nasal salt glands that allow them to excrete excess, but play it safe with them too since they consume more water than chickens and turkeys. Sodium poisoning can cause kidney damage (more so in young birds than adults because their kidneys may not be fully developed when first hatched), and heart failure.

Lead poisoning remains a serious problem in this country – primarily with wild birds and waterfowl, but can be a hazard for the free-range backyard flock or birds confined to an old coop with lead paint. Three primary sources of lead are lead shot or bullets used in hunting or target practice, lead weights from fishing lines, and lead paint chips. Chickens are more tolerant, but can die from lead poisoning as well. Lead that is consumed typically remains in the gizzard and gets ground and released into the system slowly, so many lead poisoning cases are of a chronic nature. Lameness, paralysis, weakness, wasting, and watery green diarrhea can be symptoms. However, sometimes ducks and geese can die from lead poisoning while still in good flesh, which results in an inaccurate diagnosis. Many state labs can test tissues from dead birds to confirm metal or chemical compound toxicity.

Calcium overdose is a common occurrence when people over-use calcium supplements such as oyster shell. Oyster shell offered to any female before first egg can cause kidney damage. Never mix oyster shell into feed where young females or males of any age can free-feed. Oyster shell should be provided to laying females. However, if you see ‘calcium bumps’ on your eggshells, they’re getting too much. A good vitamin and mineral supplement added to drinking water can sometimes provide enough calcium.

Vitamins A, D3 (cholecalciferol), and B6 (pyridoxine), can be toxic when overdosed. Excess Vitamin A can reduce egg production and growth rate, and cause osteoporosis. A simple top-dressing of Vitamin D3 on feed consumed by chicks has caused kidney damage in field studies. Also be careful when using rodenticides that contain 25-hydroxycholecalcoferol (from the same family of D3), as poultry, pigeons, and wild birds can also be poisoned. Vitamin B6 is toxic to pigeons at 200mg/kg of body weight by injection.

Disinfectants and fungicidal fumigants such as phenolics, quats, chlorine bleach, formaldehyde, organic mercurials, thiram, and captan cause toxicity when ingested or inhaled. The overexposure rates are too numerous to list here, so use them all with caution. Oxine is a relatively safe disinfectant and fungicide, and can also be used as a medical treatment for upper respiratory fungal infections when fogged. It’s 200 times more effective than chlorine bleach, colorless and odorless, and relatively safe to use for just about anything.

Almost all insecticides are toxic and most attack the nervous systems of all birds. One group that’s relatively safe and effective to use is pyrethrum and synthetic pyrethroids. Most poultry dust and flea and tick sprays used for the control of feather mite contain a form of pyrethrum. These products are relatively safe to use. It’s been difficult for me to find documentation that anything else is as safe. Most rodenticides (rodent control), are deadly to all birds, so poultry keepers should avoid all of them to be on the safe side.

Two common toxic gases that affect all birds are ammonia and carbon monoxide. Corneal ulceration and blindness can be caused by ammonia fumes from overspent litter. Heart rate and breathing may be affected with bronchial hemorrhage, and egg production can drop when ammonia levels rise. Growth rate of youngsters will be affected and they won’t thrive in an environment where there are strong ammonia levels. Clean, dry litter will avoid this problem. If you can smell ammonia in your coop, your levels are too high. Carbon monoxide poisoning can occur when birds are exposed to faulty ventilating systems, engine exhaust, and when open-flame brooders and furnaces are used without proper ventilation.

Household and commercial products such as alcohol, antifreeze (ethylene glycol), old solvent cleaners that contain carbon tetrachloride, fertilizers, and mothballs (naphthalene), are highly toxic and most cause liver and/or kidney damage in all birds.

Botulism is caused by a biotoxin and is a common problem among waterfowl breeders with a pond, but can also be a problem when dead poultry are left in litter to be picked at by the live birds. Very small amounts of this toxin are deadly.

Another biotoxin is algae and there are several species of blue-green algae that when concentrated by rapid growth (bloom), may poison all birds when consumed. Poisoning can cause paralysis, a dilated, distended heart, and liver damage. Anyone who keeps a pond should research the proper care and maintenance of ponds. It’s a fragile ecosystem that can help, or sometimes harm, your waterfowl.

My last group of toxins is phytotoxins (plants). Since the group is complex and ranges from deadly to chronic, I’ll just list some of them here. If any bird free-ranges and has access to nice grass or pasture, it will probably avoid these. If they’re the only things to eat though, the birds may consume them and die. Simply use this list for awareness: avocado, black locust, bladder pod, cacao, cassava, castor bean, coffee senna, sickle pod, corn cockle, cotton seed meal, coyotillo, crotalaria, daubentonia, death camas, eucalyptus cladocalyx, hemlock, jimsonweed, leucaena leucocephala, lily of the valley, milkweed, nightshade, oak, oleander, parsley, pokeberry, potato, ragwort, rapeseed meal, canola, sweet pea, tobacco (includes nicotiana), velvetweed, vetch, yellow jessamine, and yew. You should be able to locate these names somewhere on a seed packet if the seed is sold under a more common name. I would carry this list when shopping for plants and seeds for your garden.