My neighbour keeps a very smelly horse in a stable right next to my garden..what rights do I have?
I'm no expert, but I know that you'll have more luck if you concentrate on the angle of the welfare of the animal rather than on the nuisance to yourself. If you can allege that the animal is kept in dirty/cramped or otherwise unsuitable conditions, then approach your town hall to ask for the appropriate action. I'm sure there must be some law about smells etc. BUT to go from that angle you'd need to openly denounce the neighbour in the presence of a local policeman and the neighbour at the same time, and the policeman would need to clearly know the law being broken, which I think is highly doubtful.
Going from the animal's point of view will get more success.
I base this on the number of Spanish owners of dogs abandoned on small balconies all day while the owners are at work, thus they yap and crap and make all sorts of trouble for their neighbours. A trip to the town hall to complain about possible cruelty to one of God's creatures has proved effective in the past.