|Photo by Raul Lieberwirth|
Leaves, fruit, seeds, and bark contain the toxin Persin, and can cause difficulty breathing, as well as fluid accumulation in the chest, abdomen, and heart. (Bird-owners beware, avocados are also toxic to those with feathers).
There's been some debate over how harmful Avocado really is, and it's actually used in a few brands of commercial dog food (Notably AvoDerm). However, store-bought foods containing avocado generally use the non-toxic parts of the plant. I would advise you to use extreme caution before adding avocado to any home-made diet.
The lethal dose of caffeine is 150mg per kg of body weight. Just keep coffee grinds, tea bags, mountain dew, etc. out of your pet's reach, and you'll be fine.
In general, foxes are hyper enough without caffeine, anyway.
This is a pretty well-known one. Chocolate contains a substance called theobromine, which is poisonous to many animals. As a general rule of thumb, the darker the chocolate, the more dangerous it is. Chocolate can cause seizures, coma, and death. The official lethal dose of chocolate for dogs is 240 to 500 mg per kg of body-weight, but a death from a dose as low as 114 mg/kg of body weight has been recorded.
Grapes And Rasins:
These are known to cause vomiting, kidney damage, and hypercalcemia in dogs and foxes, although the exact reason why is unknown.
Green Eggplant, Peppers, and Tomatoes:
Green eggplant, peppers, and tomatoes contain toxins known as glycoalkaloids. The leaves or stem of these plants should also be avoided at all costs. As the veggie ripens and turns red (or purple, in the case of eggplant), most of the glycoalkaloids leave it, making it safe for animal consumption.
However, trace amounts of glycoalkaloids will remain in the tomato/pepper/eggplant even after it is ripe, and they will not be destroyed by the cooking process. Because of this, it is best to feed tomatoes only occasionally to prevent a build-up of toxins in your pet's system over time.
I've separated this out from the other "green" veggies, as I have additional info on it that may not apply to tomatoes, eggplants, etc.
Green potatoes contain glycoalkaloids, solanine, and chaconine, all of which are toxic. When exposed to light, the skin, eyes, and tubers of a potato can develop elevated levels of these toxic substances as a by-product of photosynthesis. Although the greatest concentration is on the surface, the "flesh" of a tuber exposed to sunlight can also develop toxic quantities of these chemicals.
The leaves, stem, and berries of the tomato plant are also toxic. (In particular the berries, which often contain 10-20 times more glycoalkaloids than the tubers.)
Care should be taken to store potatoes in light-proof sacks. Glycoalkaloids, solanine, and chaconine are not destroyed by the cooking process, so any potatoes that develop sprouts or a greenish tint should be discarded immediately.
Macadamia Nuts and Walnuts:
Poisonings from these are few and far between; signs include weakness, vomiting, and tremors.
Onions, Garlic, and Chives:
These plants are all members of the onion family, along with leeks and challots. Onions, garlic, and chives are all in the plant genus Allium, and can be potentially toxic. According to the National Animal Poison Control Center, "Allium species contain sulfur compounds known as disulfides, which if ingested in large quantities can cause gastrointestinal irritation and could even result in damage to red blood cells".
The key word here is probably "large quantities", as many resources will advise the addition of a small bit of garlic to a pet's food to ward off fleas. Still, due to the risks, it is best to avoid garlic, or to use it very, very sparingly.
Pits & Seeds from Apples, Cherries, and Peaches:
These contain trace amounts of cyanide.
Found in chewing gum, baked goods, and toothpastes; has been known to cause liver failure in dogs.
Also, for those of you who feed your pets store-bought dog food, watch your labels for the following ingredients:
Dried sugar beet residue; little or no nutritional value. Not harmful in and of itself, but a sign that the company making your pets food is cutting corners.
BHA and BHT: (butylated hydroxyanisole and butylated hyroxytoluene.)
Can cause cancer, as well as damage to the liver and kidneys. These preservatives also appear in some human foods--but remember, we only eat a type of food once in a while. Your dog or fox eats his dog food every day. If this is in his food, he's eating these harmful chemicals every day.
This is basically dried garbage; AAFCO defines it as "any and all animal and vegetable produce" picked up from basic food processing sources or institutions. i.e. garbage from hospitals, restaurants, grocery stores, etc. The produce has to be picked up sufficiently frequently so that no decomposition is evident, but still, yuck.
A preservative that has been found to be highly toxic to animals. (It was originally designed as a pesticide!). It has been associated with immune deficiency syndrome, leukemia, blindness, and cancer of the skin, stomach, spleen, and liver.
Due to protests by pet-owners, it's use is not as widespread in pet foods as it once was, but the FDA/CVM still allows it as an acceptable preservative in pet food.
Ground Almond and Peanut Shells:
Used as a cheap source of fiber, but not much nutritional value. Not harmful in and of itself, but a sign that the company making your pets food is cutting corners.
Hydrolyzed Poultry Feather or Hydrolyzed Hair:
AAFCO allows this to be counted as a protein source in pet foods. However, hydrolyzed feathers and hair are completely indigestible. If your pet's food contains this ingredient, they may not be getting enough protein.
Defined by AAFCO as "the rendered product from mammal tissues, including bone, exclusive of blood, hair, hoof, horn, hide trimmings, manure, stomach and rumen contents, except in such amounts as may occur unavoidably in good processing practices."
Rendering plants are a topic in and of themselves, but here's what you need to know: they take in the leftovers from slaughter-houses. They take in meat that's deemed unfit for human consumption. They take in restaurant and grocery store garbage. They also take in dead zoo-animals, road kill that's too big to be buried by the side of the road, diseased livestock, the works. Some (but not all) rendering companies will also take in euthanized companion animals from shelters and veterinary clinics.
They grind it all up, mix it in together, and heat the hell out of it in big vats to separate out the fat. Once all the fat and grease has been removed, they dry the remaining product and sell it as "Meat Meal".
Menadione Dimethylprimidinol Bisulfate:
Used as a cheap source of Vitamin K in inferior foods. Can cause cytotoxicity in the liver, allergic reactions, and irritation of the skin and mucous membranes.
Poultry By-Product Meal:
AAFCO: "consists of the ground, rendered, clean parts of the carcass of slaughtered poultry, such as necks, feet, undeveloped eggs, intestines, exclusive of feathers, except in such amounts as might occur unavoidably in good processing practices."
Same basic problem as meat meal.
Adds bulk, but very little else. No real nutritional value.
Adds bulk, but very little else. No real nutritional value.
A final note: Watch out for ingredient-splitting in store-bought pet foods. This is where a company will "split" a grain into two categories so that they can list a meat as the primary ingredient, i.e.:
Instead of the ingredients list reading:
Corn, wheat, chicken, rye, salmon meal...
It will read:
Chicken, corn flour, wheat germ meal, rye, corn gluten meal, wheat flour, salmon meal, wheat middlings and shorts, corn bran...
That way, it looks like Chicken is the main ingredient, even though it's not. Sneaky, sneaky pet-food companies. If your pet food has got several different permutations of corn, wheat, or other grains, they may be using "splitting" to disguise the fact that meat is not the primary ingredient.
Hope this was helpful, and if anyone knows of any other foods to avoid, please let me know!