The cage

The first cage system was built to house the egg-laying bird. The hen was to become the complete victim of her own menstrual cycle. In order to mass produce her powerful protein package for humans to eat, flock numbers were greatly increased and each individual animal was locked into a tiny cage, from which she would lay as many eggs as any free ranging hen could, and even more. This cunning idea was about to revolutionise food production techniques.
The cage became an essential component in the application of industrial mechanised processes to the treatment of animals. By caging birds, the cage itself came to represent one of the most cynical suspensions of compassion ever contemplated by humans. In order to guarantee food supply, we decided to become thoroughly pragmatic. The caging system was an emergency measure at a time when many other horrible things were happening. Its introduction was barely noticed.
By the end of the war, "battery farms" were already established. The system was based on the idea of having batteries of cages in rows, tier upon tier, with these cages promising life-imprisonment for each bird. The hen had been reduced to a biological function; far from caring for the welfare of these long time friends of humans, they were abandoned to their fate, as machines working for the egg industry. This deliberately created hell hole environment was forced on one species to benefit another. This caging system is perhaps the most anti-altruistic thing humans have ever done and it has given rise to the concept of "speciesism", in its most extreme form.