We built the ark for our first pigs back in early 2010 and it is doing really well

To start with I put extra bales inside the ark to close off some of it so they can't get lost in all the space

Once they get a bit bigger I remove those bales and they spread out to the rest of the area.
They are very much enjoying the grass - munching happily in preference to the pig nuts!
We'll take them on til they are about 85kg liveweight