seizures

Question
I have a 3 year old saint bernard and about amount and have staring having some seizures. 2 of them on separate times so i took hem to the vet and they say something with is liver due to poising. There is nothing im my house the he can poison with. So he give me some medicine for it Denamarin ones a day and  watson ursodiol capsules one every 12 hrs. he dee good for a week and the seizures stater again one each day, so i call the vet doctor and he toll me that he still geting poison. so i told him that the only stuff the my dog eat is his own dried food. So he toll me to switch the food brand and still give hem his medicine. So it has been almost a week sin i switch hem to a different food. So today may 15 start again, he had two seizures 3 hours apart.
So i don't know what to due anymore. So idid some more research about it. I found that the almost all dog food are no good for dogs, because of something on it makes them have the seizures, so i need to give my dog more nutrition food. I found this web site and i have read some of other problem pet owner are having with there dogs.  Please if you can help me with your knowledge and experience on animal  will be appreciated.
Thank you much.

Answer
This is an issue that you must work out with your vet. If you are unhappy with the advice your vet is giving you, I strongly suggest getting a second opinion from a different veterinary practice.

The one thing I do want to mention about dog food is that dry (kibble) food is often preserved with rosemary extract which is suspected to be a seizure issue for sensitive dogs. I would suggest switching to canned (like Nature's Variety Instinct http://www.naturesvariety.com/instinct_dog_can) or dried (like Real Meat http://www.realmeatpet.com/Real_Meat_Foods.html) food and avoid rosemary extract while you get a second veterinary opinion.