You may notice that, by default, horse URLs on the beta site link to their name, rather than their ID. You can also link to a horse via their id. http://beta.finalfurlong.org/horses/dark-continent and http://beta.finalfurlong.org/horses/1918 are identical. (You can see the ID by hovering over the top table cell that has the horse’s name in it, it will show up on the right of the name.)
It doesn’t matter which you use for links, but if you rename a horse (when that’s an option 
) then the link will change if you’re using the text version rather than the ID. So for babies, you may want to use the ID-based link until the name is definite.