Daily Exposure of Hooves to Water
In nature the horse goes into the water most days to drink. They don't know that their hooves need to absorb moisture but they'd rather just spend some time drinking, playing and cooling off. The absorption of water prevents the hooves from drying out which keeps them elastic and supple to maintain hoof mechanism. With lack of water on hooves they can dry out and cause lack of hoof mechanism, shock absorption, cracks and over time contraction.