Hay or Readigrass

I would give them a little bit of each.

What is ready grass?

Pure chopped dried grass is exactly the same as hay except maybe not chopped. Hay is just grass that has been cut down and left to dry in the sun before being put into bales. So long as the strands of grass are long enough it would only depend on the drying process used. There are a few drying processes, like adding salt, which would not be as healthy. It's still probably healthier than moldy hay.

Good quality hay is free from mold, dust and dampness. The best place to get good quality hay is straight from a farm. Make sure the hay is mostly green, too.

As for the Readigrass, I would only give your pigs a handful each per day. I find it is very rich and can upset my pigs' tummies, so I tend to avoid it and give them fresh hay and fresh grass daily.

I have always been told from the guinealynx'ers that readigrass should not replace regular grass hay. I second ccc's suggestion on finding a farm or a horse stable where you could buy a good bale of hay. Don't feed any hay that you even think is moldy as it will make the pigs very ill or possibly kill them. If it smells musty, don't feed it. You could use the readigrass for a couple of days until you find a good source of grass hay but not longer than that.