Older Shepherd not eating

Question
Good day,
My 10 year old German Shepherd has not been eating for a week. We have been force feeding him plain yogurt, tripe, and home made meals. We also need to give him two Glucosoime pills for his spinal disorder and 5 vitamin E pills with 1 vitamin C pill. Because he has not been getting his Glucosimne regularly his back legs are giving out. He drinks a lot of water (more then normal) eats a lot of grass, does dry heaving (almost sounds like a cough) eats a lot of grass-pukes up grass and when poo's, it it solid dark brown/black in color, usually has grass in it. Recent history of Sammy: beginning of July Sammy was poisoned by Strict 9 (we think-never proven) lawn poison by a neighbor. He nearly lost his life, had blood transfusions, IV, Charcoal. After we got him back he seemed good as new. Week ago got back from British Columbia (we gave him tick and flea medication b4 going) he was normal for the first little bit, then Tuesday came home to find him just salivating (looked same as when he was poisoned), he still had water in his bowl outside. Brought him inside after checking his heart rate which was normal (when he as poisoned it was erratic) he went straight for the toilet bowl water and just drank at least two bowls full. Today is Sunday we are going to take him to the vet tomorrow, bring in a stool sample if we can. But what I'm concerned about it why is he not eating of course and could it be that his liver is damaged from the poison?

Answer
It appears to me that your statement suggests you left your dog OUTSIDE ALONE when you went on vacation?????  If so, this is outrageous, given the fact that you have a maniac living next door who has already tried to kill your dog.  That dog MUST NOT BE LEFT OUTSIDE ALONE FOR ANY REASON.  Also, giving flea and tick medication to a dog whose system is recovering from serious poisoning is NOT a good idea.  Your dog's water bowl may have been full but he had been abandoned in the same environment where he was almost killed, and who is to say what sort of strong conditioned response revolves around this area, what this freak next door might have done to him when no one was watching, what other sorts of terror he may have been subjected to while he was left ALONE outdoors!  This is patently outrageous.

Take your dog to the veterinarian.  Have him totally evaluated, full super blood chemistry, orthopedic and neurological checkup, reflexes, abdominal palpation and, if necessary, xrays and MRI.  Asking questions on the internet won't help you.  You need to keep that dog INSIDE and go OUT with him when he needs to eliminate.  You have a serious problem with a sociopathological neighbor who is capable of god knows what.  Your dog needs to be safe.  AND CLOSE THE TOILET BOWL.  Drinking from toilet bowls can kill a dog.