Hoof Help!

I have 12 year old Rocky Mountain and her hooves has cracked really bad (we're afraid she might go lame if they get any worse) so I was wondering if anyone else has had this problem and what I can do for it. The vet said biotin may help. I've also seen some hoof moisturizing creme would any of that help?

That kind of surprises me, we have Rocky Mountain horses as well and they all have good hooves.
You might start her on a hoof supplement with her feed, plus put her on a more regular trimming schedule. Maybe every 4 weeks rather than 6-8 weeks at least till the cracks have grown out.

you have to determine whether the cause is environmental or biological

How would I be able to tell which it is??

More information would be useful... things like...

What type of environment is your horse in? Wet, dry, shifting between the two...

Is your horse getting professional hoof care? How often?

Are there other horses in the same environment or on the same diet with him? Are they evidencing similarly?

How long has this been going on? What has been done/attempted to remediate the condition? Etc., Etc.