I know that this is an older thread, but I had the same question. I recently acquired some Castor Bean seeds and have done extensive research on them. The entire plant is poisonous. The seeds are the most dangerous. For the most part, however, the seed is usually only toxic if ingested with the casing crushed. If the seed is ingested whole, it will normally pass without incident. The exception to this is poultry. Since chickens ingest small gravel and similar things to break up their food prior to it moving on to be ingested, the likelihood of them becoming poisoned is ten fold. This plant is commercially grown for Castor Oil production....but the really dangerous substance found in the seeds is Ricin. I am sure you have seen it mentioned on TV shows...as one of the most deadly poisons with no taste or smell and only small amounts needed to poison someone. The signs of which are often times not even present until 24-48 hours after ingestion.
THIS IS NOT A PLANT TO HAVE AROUND YOUR PETS AND FARM ANIMALS.
Here are the clinical signs of poisoning in animals:
Signs support nausea and include evidence of abdominal pain, bloody diarrhea, tenesmus, and dehydration. Additional signs may be anorexia, cessation of rumination, excessive thirst, weakness, muscle twitching, dullness of vision, convulsions, dyspnea, opisthotonus and coma. At postmortem severe inflammation of the stomach and intestine are evident.
Sometimes convulsions and decreased tendon reflexes are observed. After convulsions, death may result from paralysis of the respiratory center. Artificial respiration may not preserve life for long because of rapid onset of concurrent vasomotor paralysis.
In ducks, there is an ascending paralysis which may be confused with botulism. Sometimes thousands of ducks as well as geese are poisoned.
For horses, signs include trembling, sweating, dyspnea, incoordination, vigorous heart contractions, shivering, cold extremities, depression, increased body temperature, weak pulse, constipation or diarrhea, and convulsions.
Cattle may have diarrhea stained with blood.
Pigs have frequent vomiting.
Poultry show signs of depression, roughened feathers, droopy wings, greyish wattles and combs, and emaciation. Egg production ceases and premature moulting may begin.