What farm animal(s) were once housed in this weird outbuilding?

The husband and I have been looking at agricultural land for several months, hoping to find something on the cheap to work into a minifarm. Most of these places are decrepit. However, at one such decrepit place, we found a falling-apart outbuilding whose previous useful life was a complete mystery to us. Can you identify what it was used for from these pictures I took?

1. This picture was taken from several feet away to give a good frontal panoramic view. There are several very narrow chain-link fence “runs” that are tall enough to walk into, have doors, but the holes leading into the building are very small, much like a doggie-door.

2. This picture is closer up, looking into a couple of the “runs.” The small doors into the building are more visible. Each run is completely fenced in and separate from the other runs.

3. A different close-up of the runs.

4. This picture is a side view of the structure. The runs are visible on the left side of the picture, and the little “doggy” size doors open into the structure proper.

5. This picture is of the inside of the wooden part of the structure. The backside of the small “doggy” doors are visible on the left side, with the cage-like covering. The room really is that narrow, there’s no big space to the right (out of view), it’s just a wall. The building itself is rotting away.

Our best (wild) guess is that it was a dog kennel of some kind, but it would have been very small for a dog, and we couldn’t figure out why the runs would be separate, but the building itself not partitioned. Chickens would need a bigger area to run. Rabbits? It’s far too small for goats, and a cow wouldn’t fit through the gate door. The building is too small to house much of anything, most of the space is in the runs, but that would be too cold for animals to live year-round through a Michigan winter.

We’re totally stumped as to what this outbuilding was once used for. Any ideas are welcome! Thanks!