short stories - Fantasy story circa 60s about a sheltered vegetarian boy who visits a slaughter house with dire results

The boy's parents die when he is a baby and he is raised by his vegetarian grandmother in an isolated rural setting. She teaches him to cook, but dies without teaching him about the dangers of life outside his world. After her death, he goes into the nearest town, orders lunch at a restaurant, and eats pork for the first time. The boy likes the dish and he inquires from the waiter what the dish is and where it comes from. He is told that it is probably pork, but may be human, and is directed to the local slaughterhouse for a tour. As it turns out, the slaughterhouse processes people as well as pigs. In the final horrible scene, a chain is tied around the boy's legs and he is put through the slaughtering process with the pigs and other people taking the tour.

Answer

Fantasy story circa 60s

"Pig", a 1959 short story by Roald Dahl, has its own Wikipedia page.

The boy's parents die when he is a baby

Thus, when he was no more than twelve days old, little Lexington became an orphan.

and he is raised by his vegetarian grandmother in an isolated rural setting.

She was his great-aunt:

And thus it was that the infant Lexington, when he was thirteen days old, left the City of New York and travelled southward to live with his Great Aunt Glosspan in the State of Virginia.

[. . . .]

But she was an eccentric old woman, there was no doubt about that. For the past thirty years she had lived a strange isolated life all by herself in a tiny cottage high up on the slopes of the Blue Ridge Mountains, several miles from the nearest village. She had five acres of pasture, a plot for growing vegetables, a flower garden, three cows, a dozen hens, and a fine cockerel.

And now she had little Lexington as well.

She was a strict vegetarian and regarded the consumption of animal flesh as not only unhealthy and disgusting, but horribly cruel. She lived upon lovely clean foods like milk, butter, eggs, cheese, vegetables, nuts, herbs, and fruit, and she rejoiced in the conviction that no living creature would be slaughtered on her account, not even a shrimp.

She teaches him to cook, but dies without teaching him about the dangers of life outside his world.

"This is really too bad," the poor boy said, pinching her several times to make sure that she was dead. "And how sudden! Why only a few hours ago she seemed in the very best of spirits. She even took three large helpings of my most recent creation, devilled mushroomburgers, and told me how succulent it was."

After her death, he goes into the nearest town, orders lunch at a restaurant, and eats pork for the first time.

"How do you do," Lexington said. "I should like a large hominy cutlet please. Do it twenty-five seconds each side, in a very hot skillet with sour cream, and sprinkle a pinch of lovage on it before serving—unless of course your chef knows of a more original method, in which case I should be delighted to try it."

The waiter laid his head over to one side and looked carefully at his customer. "You want the roast pork and cabbage?" he asked. "That's all we got left."

"Roast what and cabbage?"

The waiter took a soiled handkerchief from his trouser pocket and shook it open with a violent flourish, as though he were cracking a whip. Then he blew his nose loud and wet.

"You want it or don't you?" he said, wiping his nostrils.

"I haven't the foggiest idea what it is," Lexington replied, "but I should love to try it. You see, I am writing a cooking-book and . . ."

"One pork and cabbage!" the waiter shouted, and somewhere in the back of the restaurant, far away in the darkness, a voice answered him.

The boy likes the dish and he inquires from the waiter what the dish is and where it comes from. He is told that it is probably pork, but may be human,

"I have to admit that I am really rather confused by what the waiter has just been telling me. Are you quite positive that the delectable dish which I have just been eating was prepared from pig's flesh?"

The cook raised his right hand and began scratching the rash on his neck.

"Well," he said, looking at the waiter and giving him a sly wink, "all I can tell you is that I think it was pig's meat."

"You mean you're not sure?"

"One can't ever be sure."

"Then what else could it have been?"

"Well," the cook said, speaking very slowly and still staring at the waiter. "There's just a chance, you see, that it might have been a piece of human stuff."

"You mean a man?"

"Yes."

"Good heavens."

"Or a woman. It could have been either. They both taste the same."

and is directed to the local slaughterhouse for a tour.

"We don't butcher pigs in the kitchen," the cook said. "That lot you just ate came from a packing-house in the Bronx."

"Then give me the address!"

The cook gave him the address, and our hero, after thanking them both many times for all their kindnesses, rushed outside and leapt into a taxi and headed for the Bronx.

In the final horrible scene, a chain is tied around the boys legs and he is put through the slaughtering process with the pigs

At this point, while Lexington was gazing skyward at the last pig to go up, a man in rubber boots approached him quietly from behind and looped one end of a chain around the youth's own left ankle, hooking the other end to the moving belt. The next moment, before he had time to realize what was happening, our hero was jerked off his feet and dragged backwards along the concrete floor of the shackling-pen.

and other people taking the tour.

The conveyor-belt seemed to be travelling right over the top of the cauldron, and the pigs seemed to be dropping down one by one into the boiling water, and one of the pigs seemed to be wearing long white gloves on its front feet.