There is no federal law that protects chickens during slaughter, leaving the USDA free to make its choice based on money.
Chickens enter the slaughter line when a worker shackles them upside down by the feet, after that the birds reach the throat-cutting machine or worker. The fastest way to kill them here is to sever both carotid arteries, which leads to unconsciousness in two minutes. That doesn’t always happen. The carotid's are buried deep in chickens’ neck muscles, so cutters sometimes miss them and cut one jugular vein instead, which leaves the birds conscious and suffering for eight minutes. The birds are left hanging for 90 seconds to bleed out.
The next station is the scalding tank. Chickens are dunked into boiling water to remove their feathers. At this point, many of them are still conscious — they are boiled alive. Some birds twist their heads up and avoid the throat-cutting machine. Slaughterhouse workers call these fully conscious birds “red skins” because they are still full of blood when they hit the boiling water. In one year that the government kept records for, 3,121,617 red skins were dropped into scalding tanks.
If the bleed-out time is shortened, even more birds will feel the boiling water.