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Avocado
"Toxicity to animals
There is documented evidence that animals such as cats, dogs, cattle, goats, rabbits, rats, birds, fish, and horses[15][25] can be severely harmed or even killed when they consume the avocado leaves, bark, skin, or pit. The avocado fruit is poisonous to some birds, and the ASPCA and many other sites list it as toxic to many animals including cats, dogs, and horses.[26] Avocado is an ingredient in AvoDerm dog food[27] and cat food.[28] However, the ASPCA has declined to say whether this food is safe or not without knowing the details of how the avocado is processed.[29]
Avocado leaves contain a toxic fatty acid derivative known as persin, which in sufficient quantity can cause equine colic and, without veterinary treatment, death.[30] The symptoms include gastrointestinal irritation, vomiting, diarrhea, respiratory distress, congestion, fluid accumulation around the tissues of the heart, and even death. Birds also seem to be particularly sensitive to this toxic compound. Feeding avocados or guacamole to any non-human animal should be avoided completely. Negative effects in humans seem to be primarily in allergic individuals."