I read this in the UK back in the 1980/early nineties. It was a library book so it was sort of mainstream I guess. The main protagonist is a teenage boy with a younger sister. He has now aged out of a certain ceremony where silver ribbons are given to the best and brightest children. These children are then sent to the Silver city where life is as it was before the destruction of everything. His little sister is chosen to go. I can't recall any names unfortunately but he basic premise was quite haunting. All non human animals are extinct, mute and mentally disabled humans are used as beasts of burden and sources of meat. They are referred to as stock or meat. It is accepted that they have no souls and are not people. This boy discovers that the children chosen for the silver city are rendered mute and lobotimised and put into the stock to keep the gene pool healthy. He sets off to find and maybe rescue his sister. I feel that this was a smallish book but not a short story or part of an anthology. I don't recall the protagonist much as he was frankly a typical teenage male character - amazing good with guns and his lover was, I think, a prostitute, possibly called Lori or some such.
That will be Neal Barrett Jr, Dawn's Uncertain Light,
I thought I read it a long time ago, but can't remember much, except that the young hero cottons on to the fact that stock and people are the same. Istr that a female "stock" is called a mare, and there's a scene where the boy sees what he thinks is a woman being raped, then looks again and sees it is a mare. However, DUL is a sequel to another novel Through Darkest America, and that scene is mentioned in both books.