There's nothing better than a running partner that never complains, doesn't care far you run, is happy with any pace and is always in a good mood! Mine is named Chip. A mix of black Lab, Schnauzer and a little crazy thrown in there. She has endless energy.
Thinking of getting a dog to run with? There's no best breed as I would say it's more of a best size. I've had large and medium sized dogs. Large dogs are great for 10km or so but Chip who's about 30 pounds can do the long distance and wants more!
FOOD & WATER
Just like you your dog needs and water on the trail. If there's no creeks around I give her water from my bag and pack her some kibble in a Ziploc. If your going long you may want to invest in a pack for your dog so they can haul their own stuff.
Just like us the hazards on the trail effect your furry friend. Heat is a big one for dogs. Even if you know they can do the distance when it's 25 + degrees don't take them out too long! Cactus is another in my area as I've pulled a few of of my dog. Predators are another bad one. Dogs love to chase the unknown through the bushes. Make sure you have good recall on them as they can find something bigger than them!
Some of my trail running friend are the dog whisperer! And they bring lots of dogs.