What is the significance in the story of the continual reference to pigs and hogs, and how are they a metaphor enhancing the theme of "Revelation"?

Pigs, hogs, and even warthogs are used symbolically in various ways in Flannery O’Connor’s short story titled “Revelation.” Among those ways are the following:

• They function as symbols of pride.  Mrs. Turpin takes pride in raising pigs, just as she takes pride in so many other details of her life and personality. She is a fairly prosperous pig-farmer and is up-to-date on all the latest innovations in the field (such as concrete pig-pins). O’Connor, who continually mocks pride in her stories, must have enjoyed the humor of creating a person who took pride, of all things, in pigs. Since pigs have usually been regarded as among the least appealing of animals (at least until they become ham and bacon), O’Connor would have enjoyed the extreme irony of making a human being proud of her association with pigs.

• Whereas Mrs. Turpin is proud of her pigs, she is rather judgmental and condescending toward most of the other people around her (except her beloved husband, Claude, whose name links him with earthy simplicity). Mrs. Turpin often treats other people as if they were pigs, and she often regards her pigs as prized possessions.  Indeed, it is because they are in fact possessions, which can be used, that they are so important to her.

• Pigs are often thought to have voracious appetites, to spend much of their time wallowing in mud or other filth, and to appear (in the words of the Oxford English Dictionary) “boorish, coarse, [and] obstinate.” For all these reasons and others, they can be symbolically (and literally) associated with the world and with such worldly qualities as greed, gluttony, and laziness. It isn’t as if Mrs. Turpin is proud of raising horses or dogs (generally considered more attractive animals); she is proud of raising pigs.

• Part of O’Connor’s “point,” in this story, is that human beings have little reason to be particularly proud of themselves. Seen from a certain point of view, we are all pigs: we are all self-indulgent, greedy, spiritually lazy, and soiled by sin. Indeed, when real pigs actually do appear in this story, they seem far more attractive than some of the human beings we have witnessed, and they definitely seem more attractive than the ugly, absurd thoughts percolating in Mrs. Turpin’s highly prejudiced mind. Thus, near the end of the story, O’Connor describes a bunch of baby pigs gathered around their huge mother:

They had settled in one corner all around the old sow who was grunting softly. A red glow [from the sun setting] suffused them. They appeared to pant with a secret life.

In phrasing such as this, O’Connor (in an added irony) suggests that the pigs are behaving more naturally, more in accord with how God created them to be, than many of the humans (and especially Mrs. Turpin) have behaved. In a further example of O'Connor's irony, there is actually something beautiful about this depiction of the pig and her piglets (actually a hog and her shoats).

Although pigs, hogs, and warthogs function symbolically in various other ways in the story, the functions just outlined are hard to deny.