In Equine World, horses never need to pass away or be forgotten.  Their stats (no pictures) can be sent to Katie M. at any point in their lives, and they can live in virtual bliss in the Equine World Retirement Pastures forever. 

Horses who are retired may never be brought back into circulation.  Retired horses have no owners; they cannot be bred, showed, bought, or sold. 

To retire a horse, complete the form required and email it to Krystle
  Your horse(s) will be added to the site promptly; however, you need not wait for a response.  As soon as you have sent your retirement form, you may remove the retired horses from your Mandatory Registry list.