How is this even possible?

There is an oft repeated story in my family which illustrates the ingenuity of my paternal grandfather. He had a 45 acre homestead in Oak Creek, Arizona which has since been sold and become Slide Rock State Park. It is a remarkable piece of property, a lot of which he devoted to apple orchards. but back in the day Frank Pendley had a problem with mountain lions getting into his pigs. He had a family of nine kids to support which was no easy task in those crop-dependant days before grocery stores were handy. So he tried all sorts of things to keep the cats from getting at his pigs. He strung pie plates and pieces of tin along the parameter of the enclosure. He stood guard at night. He tried various booby traps. None of them worked. Finally he put a little unweaned German Shepherd puppy that did not yet have its eyes open in with his sow right after she gave birth to a new litter. The newborn dog was just happy to have a warm spot and a meal. The pig seemed indifferent, and accepted the pup as one of her own. I've heard stories of how comical it looked to see that little puppy nursing between it's sibling pigs. But as the dog grew up (albeit with a bit of identity confusion) it would bark any time a cat got close which would warn my grandfather to come running with his shotgun to protect his animals.

Ok, so I am familiar with the idea of interspecies parenting.

But how the heck do you convince a tiger that baby pigs are not food???