Do you have to use whole milk?

If you happen to have either half and half or regular cream, you can add in a few spoonfuls of that to your milk to replace the fat of whole milk. The dough for kolaches is supposed to be a very soft, rich one- which comes from the butter and fat in the milk. You could use 2% milk, which contains half the fat of whole milk though- without noticing a lot of difference. I would not recommend either skim or 1% though. This dough needs the fat.

I think you'll be ok with 1% or 2% milk. I wouldn't use skim. It's too lean which could result in a drier kolache.