A great quotation from Pete Ramey...
"Remember that all foals are 'born crooked'; they've spent their whole
life wrapped up in a ball! Movement is essential for straightening them
out. Unless directed by a veterinarian for a specific injury or reason,
do not confine foals in stalls. Every aspect of their proper development
requires movement. I also firmly believe that if every foal received
routine competent hoof trimming from the very beginning, angular limb
deformities in adult horses would virtually disappear from the horse
world; I've seen this with my own eyes in my own clientele. Birth
defects do happen but they are far more rare than most people think.
Instead, what is very common is that foals get off to a slightly wrong
start, this skews the hoof balance and then their joints, ligaments,
tendons and muscles are allowed to grow and form on the imbalanced,
neglected hooves. Eventually the horse matures and the conditions are
effectively permanent.
Most people think that hoof trimming for adult horses is a necessity and foal trimming is a luxury. If anything it should be the other way around."