i have a 14 year old english setter. within the last year he is not the same, he paces back and forth.He also has mood swings, Ifanybody comes over my house he growls at them and he wants to bite them.He even will try to bite and growl at my wife and kids. Healso has a hard time getting up the stairs.Sometimes he is real peppy other times he is not.He has never been like this, what could it be,I cant trust him with people.
It is possible he is becoming senile. At this age they also start to loose their senses including sound, sight and taste. This makes dogs a bit nervous. vetcare