Re: cracking hooves
Here is a link to a recent newsletter from Dr Kellon about cracking hooves. You can subscribe to receive her newsletters via email.
I thought the timing of receiving her newsletter just before your question was excellent. Because your horses live in a red clay area I would imagine that they frequently have their hooves coated in that red clay soil. IME clay will absorb moisture, meaning it would dry those hooves excessively. In this case you might consider using a barrier on the hoof walls, such as Keratex. I used to board a horse in Northern VA and I used "Mushers Secret" which is a waxy product designed for dog paws. It has to reapplied more often than the Keratex.
Bonnie Snodgrass 07-2016
ECIR Primary Response
White Cloud, Michigan, USA