The Black Fawn by James Arthur Kjelgaard audiobook.
Bud Sloan was an orphan who had been 'sold out' of the orphanage to work on a farm once he'd been old enough to labor. The farm where he was to work was owned by an aging farmer and his wife who had raised a large family and were now left alone.
One day, after his chores were done, Bud wandered into the woods nearby and with mouth agape, he noticed a newborn jet black fawn all alone and apparently confused in his new surroundings. Bud resolved that day that this baby fawn was just like himself, an orphan, and would be bound to him in spirit. But many obstacles would keep the two separated, and the black fawn would eventually become the target of the local hunters.