After building the fence line for the mini track system, we put in 10 tons of pea gravel. The horses have to walk over the pea gravel to get to their hay and back again to get to their water. The pea gravel helps stimulate and support the back of their feet. I've seen it also help them naturally exfoliate the dead sole material when it's ready to come off. As as you can see from the video, Harley loves to roll in it.