One thing i read somewhere or heard is that they stop feeding the animals a few days before they kill them because they found it makes no difference to their weight when killed. So basically, they stave them, then cut their throats. And chickens, are kept in cages with many others chickens. A comparison was made to a person being born in a elevator with 16 or so other people in it, and living there its whole life until a few days before it's slaughtered where its food is cut off too.