a wide slatted barn sounds like a cold place for a steer to lay down.

I won't argue that.  I've heard comments to the effect that a slat barn really shines in the summer when it's hot.  Along that same line of thought, I've heard that an unwanted effect of a bedding pack is that it gives off heat in the summer as well as the winter, thus unwanted heat is generated in the summer.  Any thoughts on this?