Webster tells us below that a slaughterhouse is "A house where beasts are butchered for the market", making it sound innocuous, generic and palatable.
What a naive clod he is. :)
The modern-day North American slaughterhouse is so much more. Some would say they are, in a way, an icon of what more critical people world corelate to "the American Way" of production and consumption. But I digress... What I came here was to tell you how a meat packing plant and the modern-day slaughterhouse, functions. In great detail. Using big words and graphic imagery.
** This writeup is rated "M" for "Mature" due to graphic depictions of death and dismemberment **
For nigh on 25 years, my father has worked in the meat industry; first in a meat packing plant, and then as a Federal Meat Inspector for the US Department of Agriculture. This is what I've picked up on about the industry over the years from being his child; the focus here is on beef cattle, though the processes are probably similar for other beasts. Processes described herein probably vary from state to state and country to country.
The cattle's trip through Bovine University begins in a small lot immediately adjacent to a door of the slaughterhouse. The size of this "tendering lot" varies from the processing size of the plant in question, but usually can hold enough animals to supply an entire working shift with raw materials.
From here, usually one bovine is taken at a time either to a corner of the tender lot or (in the case of larger operations) through a cattle chute to a smaller "dispatching" pen or to a section of the slaughterhouse known as the kill floor. This is where the carnage begins, in that this is where the animal is actually killed. Depending on the style of meat being processed that day, that cow may or may not be injected with pineapple juice prior to their death.
It's not actual pineapple juice, but a concentrated extract of the acids in it which are a very powerful natural meat tenderizer; They are injected while the animal is still alive to ensure that the tissues are saturated with this as evenly as possible. As soon as the chemical is injected, it begins to break down the tougher sinews of the animal's muscle fibers, as well as quickly destroying the liver, kidneys and heart. After the injection, if the animal is not manually dispatched, it will pass out and die within a few hours. Not all slaughterhouses do this, and the practice is slowly going out of fashion due to the potential pain involved, though some houses still continue to do it.
The Federal Humane Slaughter Act is the law that stipulates the procedures that must be followed in killing these animals. It says that the animal to be dispatched must either be rendered unconscious prior to the delivery of the fatal blow, or the blow itself must render the animal immediately insensible. The three main methods used are firearms, electricity or chemical means.
Firearms - This is the method I am most familiar with -- in the western United States the common "firearm" method doesn't use bullets at all, but instead uses a large, non-expanding metal rod fired through the immediate cognitive center of the the brain (though, due to the large size of the bolt and the relatively small size of the cows brain, usually the entire brain is obliterated). In this method there is little danger of damage to the carcass itself, and death is, understandably, instantaneous.
Electricity - Another common method is the use of electricity. The animal is either killed immediately by electrocution, or simply stunned/rendered unconscious for later killing, usually by "sticking", the slitting if the throat and forearms while hanging by the hind legs.
Chemicals - This has fallen out of favor over the years due to the dangers of the chemicals remaining in the tissues of the animal, and thus may be harmful the the consumer. However, my limited knowledge of the process alludes to it being much like euthanizing of a house pet in that an intravenous solution is administered which causes cessation of mental and pulmonary activities. While death takes a few seconds, the numbing effect of the chemicals in question most likely renders the cognitive centers of the brain inoperative.
Now that the animal is dead, it is taken to a draining chamber where the carcass is shackled by the hind legs and hoisted. The carcass is either slit on the jugular or decapitated altogether, and the front hooves are cut off. The animal is then allowed to drain for a period of time. I have heard that the carcass may sometimes be electrified to contract the muscles and squeeze out any remaining fluid, but I have never seen it.
After draining, the carcass is hoisted onto a meat hook (usually on a rack, crane or line) where the rear hooves, tail and genitals, if applicable, are removed. The carcass may also be skinned and drawn (gutted) in either this part of the process or the following process.
The carcass is then moved into a "cooling" room with many other carcasses where its temperature is quickly cooled to a point where bacteria have a harder time growing. Here is also where a governmentally employed Inspector will examine the carcasses for a variety of things including improper preparation, foreign materials on the carcass (most frequently dirt or animal feces), and traces of disease.
Once cooled and inspected the carcasses will move to the "slabbing" room where the individual "sides" of the meat are removed from the backbone and the limbs are also removed. These parts are hung separately and, if required, again subjected to inspection.
From here, actual methods vary from plant to plant and the type of product being produced. Generally speaking, though, the backbone will be send to an AMR (Advanced Meat Recovery, also known as Advanced Meat/Bone Separation) facility, which is a mechanical apparatus that allows trace meat to be recovered from otherwise inaccessible nooks and crannies in the bone structure of the spine.
If the plant is producing a Chopped and Formed product, such as lunch meats, sausage and hot dogs, all of the remaining carcass will be trimmed by hand of meat and the bones also sent to an AMR facility as the actual shape and state of the meat is not important since it will be pulverized anyway. For whole meat products, preparations are seldom done in the plant itself; the raw parts (side and legs) will be sent to an advanced processing facility or a butcher.
Raw parts are packaged according to type, use and destination. They are then chilled to either a frozen or near-frozen state. The actual packaged product is usually inspected again to make sure packaging is up to code and temperature is maintained. From here they are ready to be shipped out to their final destinations.
Modern day facilities, especially those that are corporate-owned by megacorporations like Hormel, Tyson or ADM, are capable of processing millions of animals a year, with estimates on total cattle processed in the US putting the number at tens-of-millions of head (a large part of that number is for export).
When people think about slaughterhouses, they almost always have images from The Jungle in their heads, with thoughts of amputated limbs and rats on the conveyor belt. While this is simply not true, they are still anything but pleasant places to be in, especially working in the early parts of the process. In fact, when I first toured a plant when I was six, I found it absolutely terrifying. Now that I'm older it no longer terrifies me, but I still find it a little disturbing.
Slaughterhouses are, by and large, efficiently run and tiresomely clean places; production laws have been continually refined since the passage of the Pure Food and Drug Act to the point where there is a thriving business of cleaning companies that only do slaughterhouse sterilization.
That having been said, there is still one thing that always haunts me about them -- the smell. If you have ever butchered raw meat yourself, you know the smell of blood; well, imaging that half-a-hundred carcasses all around you making that smell.
Some of the more militant Animal Rights Activists will spin all sorts of tails (pun intended) of the barbary of a modern slaughterhouse, most of which is simply not true as the processes are largely humane and painless. But still, if you want to make yourself seriously consider going veggie, take a tour.
P.S. - Yes, I still eat meat.