The Great Lad
A Dog Called Gelert and Other Stories.
Wyn Jones was driving home his sheep during a blinding storm when a mini avalanche trapped him. His dog, Moss, desperate to make it to the farm for help, faced his own perils in drifts too deep for him to climb and creeks hidden by layers of snow. When Moss finally made it home he stayed only long enough to steel a leg of lamb to take back to his master, which gave Wyn the strength to survive until rescuers found him.