These dogs were the result from mixes of Bullenbeisser and other similar breeds. The Akita Inu is one of the most dominant dog breeds. Chihuahuas are one of the smallest lap dog breeds. Toy Poodles have one of the smallest litter size of all breeds. Irish Wolfhounds are the tallest of all dog breeds. Belgian Malinois exhibit energy levels that are among the highest of all dog breeds. They are one of the few naturally spotted breeds of domesticated cat. The book explains Coren's theories about the differences in intelligence between various breeds of dogs. This is a list of dog breeds, including extant breeds and extinct breeds and varieties. The Rottweiler is one of the oldest of herding breeds. PRA can occur in most breeds of dog including mix breeds. It is well muscled and less bulky than most other Mastiff breeds. Tollers are the smallest of all the retriever breeds. It is one of the oldest breeds of pigs in England. This is a list of domestic breeds of sheep.