But still, egg and dairy animals are culled when productivity drops. The human equivalent would be killing all male babies, and females after age ~40.
This does not seem more "humane" than the human equivalent of meat farming, where all human offspring would be harvested at age ~15.
And pregnancy is _hard_ on animals (including humans), it changes your physiology and psychology. Even if we take for granted that a cow isn't as conscious as a human (IMO consciousness is a sliding scale, not a binary), then they are still being primed for giving birth and taking care of offspring which never comes. Imagine doing that to a human - it's a definite form of cruelty.