Pig poop, is also a noun, by those of us who have walked in it, washed it off our boots, and never been able get away from its distinct and unforgetable smell.
Pig S*** in the venacular and informal speech.
(I got a 50 year high school graduation class reunion comming up; one of the people spent his youth on a hog farm; he became an IT person and has never stopped talking about pig s***; every time we've had a class reunion over the last 50 years he has talked about getting away from the hog farm and the pig manure).
Pigs poop (a really childish way to talk about the pig's waste disposal processes) the same way as other mammals.
Mammmals, unlike birds and other reptiles, have separate systems for removing solid and liquid waste products from their bodies. 'Poop'* is solid waste (urine is the fluid waste). The solid waste disposal system extracts nutrients and recovers the water used in the processing and then eleminates the waste at the end of the water recovery process. The results contains both the by-products of nutrient breakdown, and additional substances which are no longer useful to the body.
The pigs digestive system is a lot like the human beings.
In the reptile and the bird, a close cousin, both soild and fluid proceed through out the same system. The single organ is called the cloaca, after the famous open sewer in ancient Rome.
*pig manure is a better description; feces is generally reserved for human mammals.