Allow me to state at the outset of this that I am a cat person, I have never owned a dog.
I do like dogs, as I like human children, as long as they belong to someone else...
I also respect dogs very much.
HOWEVER, I STRONGLY advise NOT taking a dog on Camino for several reasons:
1. Any breed of dog must take multiple strides to keep up with their human's single stride. This means that while YOU might walk 775 Km from St. Jean Pied de Port to Santiago, the poor dog must walk three to four times farther (in dog strides), or more if a tiny breed, to accomplish the same result. This is IMHO selfish and very cruel to the dog. Of course, the poor dog, being loyal will follow their owner into hell... YOU, the human, are responsible for their health and wellbeing. This responsibility includes not leading them into a hazardous situation.
2. Any dog, even large breeds, will suffer injuries to leg muscles and connective tissues from the ultra-long walk. This is not the usual twice-daily walk in the park. Your dog is likely much less prepared to walk several hundred kilometers than you are.
3. Any dog can pick up parasites, ticks, leeches, etc., including some carrying life threatening consequences, while walking through wilderness. Veterinary care is not as readily available as human care along the Camino routes. Why take the chance?
4. As a volunteer at the Pilgrim Office for the past two years (I go again in July for a month) I saw a pathetic variety of dogs (all breeds) who arrived with their paws bandaged, or all torn up, and some bleeding and unattended. Many arrived limping, or walking in apparent pain. None were carried. All were compelled to walk, no mater how apparent their injuries. I always offered fresh water in a clean stainless bowl. It was shocking to see owners who did not even have a bowl for their dog to drink from. Again, IMHO this is very cruel to the animal.
5. Dogs are not designed to walk these long distances over "improved" surfaces on their foot pads. They are designed to walk on unpaved surfaces, not concrete, asphalt, and cobblestones. To compel them to do so is IMHO cruelty.
6. It rains, a LOT, in northern Spain throughout most of the year. You may wear a parka or poncho. What about your dog? Dogs can get hypothermia and catch pneumonia as well as humans. How about being considerate of your pet's health and well being? A day filled with rain and mud is miserable for a human pilgrim. How do you suspect the dog feels?
Lastly, and tangentially related. DO NOT EVER allow a dog encountered in a small hamlet or village to follow you!
Last year during my month-long volunteer stint at the Pilgrim Office, we had two very cruel and heart-wrenching instances of couples trailing a dog they claimed was not theirs, arriving at the Pilgrim Office. In both cases, they stated that they were walking through a small village "about four or five days back" when the dog started following them. These dogs were clearly working country or farm dogs. They did NOT have collars and were NOT chipped. The pilgrim couples inadvertently lured and led the dogs into straying from their home territory.
You must understand that, in parts of Spain (and likely in many other countries as well), country and farm dogs are animals, NOT pets! They are not treated like our domestic pets. These animals typically live out of doors, and do not receive the veterinary or grooming care that we lavish on our pets. They are WORKING DOGS. You may or may not agree with this, but it is a fact.
The couples arriving at the Pilgrim Office blithely abandoned the poor farm dogs in the city, stating that, as the dog was not theirs and freely followed them, they were not responsible. They literally just walked away into the crowds, leaving the dog to its own devices. THAT IMHO, was the ultimate in cruel, selfish behavior. I hope never to see it again. But it happened twice in as many weeks last summer.
These "nit wits" failed to realize that once the dog got more than a kilometer or so from their normal surroundings, their sense of smell and ability to recognize "home" was diminished. The poor, confused, animal had no alternative but to follow the human. In allowing this, the human created a new master-pet bond. The pilgrims thought this cute and amusing. But they condemned the poor dog. THAT was completely stupid and selfish.
In the end, in the evening, and with no one else showing up claiming the dog, in each case, and after seeing that the dogs were watered and fed, with the help of local restaurants, we were compelled to call the local animal shelter. Fortunately, we located one that operated a "no kill" shelter. However, since both dogs wore no collars and we could detect no chips about the shoulder blades, their fate was completely uncertain.
So please, if you are a dog owner
LEAVE YOUR PET IN CARE WHILE YOU ARE ON CAMINO.
If you are on Camino and a dog starts to follow you please shoo them away firmly and without striking them. This has happened to me at least three or four times when walking through a small village or hamlet. NEVER allow a dog to follow you more than a few hundred meters.
Shout at the dog to: "Va a la casa! (Go home!) Wave your arms about, raise your voice to a command tone. But, DO NOT allow a dog to follow you beyond the hamlet or village in which they appear to live.
Allowing, encouraging, or enticing any animal to stray from their normal home is cruel, inhuman, and insensitive to the animal. Please do not do it, or if you see it happening to another pilgrim, please convince that pilgrim to persuade the dog to return home.
I hope this helps.