"The sunny slow lulling afternoon yawns and moons through the dozy town. The sea lolls, laps and idles in, with fishes sleeping in its lap. The meadows still as Sunday, the shut-eye tasselled bulls, the goat-and-daisy dingles, nap happy and lazy. The dumb duck-ponds snooze. Clouds sag and pillow on Llaregyb Hill. Pigs grunt in a wet wallow-bath, and smile as they snort and dream. They dream of the acorned swill of the world, the rooting for pig-fruit, the bagpipe dugs of the mother sow, the squeal and snuffle of yesses of the women pigs in rut. They mud-bask and snout in the pig-loving sun; their tails curl; they rollick and slobber and snore to deep, smug, after-swill sleep. Donkeys angelically drowse on Donkey Down."
Dylan Thomas: Under Milk Wood - A Play for Voices
Read the whole text at Project Gutenberg, or, even better, buy the book or borrow it from your local library.
I read it in high school, and it made a deep impression on me, as did a collection of short stories by Dylan Thomas as I read them during my early university years. I had forgotten about this part with the pigs, though, until I came across a quote from it on PiggyPoop.com. (Yes, it's exactly what you think - natural fertilizer made from piggy excrements. But the recipe on their site for "Piggy Poop Tea" is NOT what you think.)