The slats were gone years before the rubberized surface. From what I remember with a conversation with Sharon, she said originally they put a few slats on contacts and other venues followed, then she realized that if the surface was slippery enough that dogs needed slats going up, dogs jammed toes coming down, so they were removed. The other venues kept the slats. You may notice that the other venue slats have diminished in size to the point that they are just token now. The slatless contacts were in place when I started NADAC in 1997/1998, but the surface was still paint and sand. So I am thinking it was either at inception or soon there after. The rubberized surface came in somewhere around 2005.