Dead cats feeding living cats - rendering plant

If proof were needed-and it isn’t-dead cats are used at rendering plants to provide pet food which then feeds living cats. Obviously many other animals are incorporated into the rendering process but domestic cats are and sometimes they have collars on and they are euthanized cats often. That means there are drugs and pesticides in and on the cat. These go into the rendering process and are part of the food chain which can end up being eaten by living domestic cats and I presume livestock and even people.