Look it's been a while I admit...
But looking through
the Ol' Ammo Box again after over a year and I noticed horses have been nerfed hard. Sure there is a remnant Rider specialty still (PG p50), which is a Mobility (AGL) specialty rather than a full skill fair enough. Like maybe two other mentions (PG p86-87 and p147)? Oh, and they can carry either a second rider or 25kg and are now considered a "vehicle" so are the first line on the Vehicle Table.
But hey, not even a stat block - admittedly there are only 4 animals listed all of them potentially aggressive, but cavalry has been given short shrift it seems.
And yes, I know there are pros and cons on post-apocalyptic cavalry, as I wrote what I thought was a reasonably comprehensive article on the subject a few years ago:
Horsemen of the Apocalypse.
Maybe I'll have to update the old article to 4E...