My elderly neighbour keeps feeding my dog god knows what through the fence. My dog has a very sensitive stomach and the slightest change in diet/certain treats give him the runs. I've asked my neighbour twice (politely) not to feed him anything. Last time I asked what he'd given him, and he said it was sausage. My dog had diarrhea for two days after! I stopped letting my dog out in the garden unattended too which stopped him from being able to feed him anything. However this morning I was outside with the dog, pottering about doing some gardening. I was behind the shed, out of view from my neighbour. He must have thought I was inside. I heard him call my dog to the fence, and when i peeked my head round I could see him feeding something to my dog. I shouted my dogs name and my neighbour almost jumped out of his skin, and he quickly walked back inside his house. I'm absolutely fuming, but I don't want to cause any conflict as we have always gotten on apart from this issue!!! Should I say something to my neighbour or should I just leave it and make sure my dog is kept away from the fence?