@vogelcommando will of course know better than most of us, however I have never seen C. alector within the US zoo circle, whereas C. rubra is fairly common. Of course that doesn't mean this can't be an alector, but personally I'd lean more towards rubra strictly due to what I know is around.
I also think it could be C. rubra, but from close-ups of this photo it doesn't seem like the bird has a sizable knob on its bill, which seems unusual for rubra? However, it would be less unusual for Yellow-knobbed (C. daubentoni) or Blue-billed (C. alberti); the caveat would be that both species are less common in private US zoos than rubra (blue-billed perhaps absent from them altogether).
As @Coelacanth18 mentions, I did a zoom-in crop of the head, and there's no visible knob. The beak appears to be a pale yellow, possibly blue-ish, at the base. When I walked back by it was in the house/box thing, so I wasn't able to get another photo.
