[quote=@Orcus]
<Snipped quote by ClocktowerEchos>

Along with horses i think mules went; but Brahmin, or a giddy-up-buttercup works, which is a tiny robotic pony.  
[/quote]

There is no canon mention of mules and donkeys being extinct. In Fallout, you can find a recently-dead mule. In Fallout 2, there is reference to mare's milk being in good supply. In Fallout New Vegas, the Dead Horses obviously know that horses exist. In real life, wild horses are still [i]astonishingly[/i] common out west. A nuclear apocalypse would cause some upheaval in their numbers, but if [i]dogs and cattle[/i] can survive, a horse could too. To think that [i]every single species of equid in America[/i] is extinct is, quite frankly, silly.