I feel like human nipples just because it would be way more convenient. Getting the whole extra torso under the horse body seems like a pain. I need someone to draw both options now so we can discuss.
Eta: wait wait, are centaur babies human baby sized with proportionately small horse parts, or are they baby horse sized with a bigger human parts to match? That could change my answer.
I feel like they should be colt sized, because in most depictions centaurs don't seem to actually have accessible human genitals, so they should be gestating in the horse body and not the human body.
But they’re not literally half human half horse, they’re fully centaur.
So there’s no human genitalia or horse body, only centaur genitalia and centaur body. Where the centaur genitalia is on the centaur body could be anywhere, ex. horse based locale dong but human based mammaries.
I'm guessing the human ones as you'll need to hold them until they're strong enough to hold up their own heads. Maybe then you switch to the horse ones for convenience
you’ll need to hold them until they’re strong enough to hold up their own heads.
I don't see that happening. Do you have any idea how much a horse, even a baby one, weighs? It's not likely a mother centaur is strong enough to carry her baby to breastfeed it.
I think if it was the only way, centauri women would have an evolutionary advancement in the muscles of their upper body. Like kangaroos that are used to carry their kids in a belly pocket. And kangaroos punch like a motherfucker.
It would be funny to see all centauri women be built like MMA fighters and men be thin like a matchstick.
I think the writers across centuries made a pact to not picture a female centaur because it leads to a lot questions like that, and it's sexually confusing and can lead to assumptions the writer has a thing for fucking horses.