How can a vet tell how old a horse is by looking at its foot?

Question: How can a vet tell how old a horse is by looking at its foot?
- Keywords:
  age,
  foot,
  horse,
  vet
Asked by sybbag to Charlotte, Jo, Kevin, Louise, Valeria on 13 Jun 2012.
- Kevin Mahon answered on 13 Jun 2012:
  
  I may be wrong but I doin’t think this actually works, usually vets tell a horses age by looking at their teeth!
  
  The hoof usually is used to tell us about the horses condition – horses in good health overall will grow stronger hooves faster.
  
  But seeing as factors such as diet, environment and sometimes even the breed of the horse effect hoof growth, I think it is unlikely that this is the sole measure a vet uses to determine its age.

Question: How can a vet tell how old a horse is by looking at its foot?