These houses are usually open to the public but people (apart from zoobuffs) rarely enter them. You can look through the glass/perspex windows into the stalls/hardstanding areas. Because they are rarely visited some antelope etc living in them are quite nervous and will dash outside if suddenly surprised.
When I visited last year, I was really surprised at how good this area was. There was no one around so I had the whole Zebra/ Antelope House to myself. The animals seemed a bit suprised at first but they settled down within minutes. It was really great to get up close to an animal such as a Roan Antelope. The only thing was I didnt take any pictures as I didnt want to spook them.