It has been confirmed that Snake can steal wolf pups in Metal Gear Solid 5: The Phantom Pain and train them to do his bidding through the a system in the Mother Base. According to Konami's Community Manager, Robert Peeler, you can do whatever you want when you come across the wold pups.
Speaking with Siliconera, Peeler detailed the interactions Snake can have with the pups once you come across them.
“Now, you can do whatever you want here. You can pick it up, ignore it, shoot it if you’re heartless… but really, the best thing to do is send it to Mother Base using the Fulton Recovery System.
These pups can be trained back at mother base, and help you in future missions. They can bark to provide a distraction, or sniff out decoys among real soldiers.”
It hasn't been detailed how many times we have the opportunity to come across the pups, but we have seen full grown wolves in the game alongside snake.