In the mission Horse Flesh For Dinner you steal the 3 horses listed below.
The Dark Bay Turkoman
The White Arabian
The Black Arabian
By feeding one of the horses around 40 of any horse food it will be at bonding level one, the most important of these horses has to be the Dark Bay as the others can broken/stolen at the start of chapter 2 whereas the Dark Bay is epilogue only.
Update: Feeding the horse peppermints are the best, it only takes around ten to bond with it.
This still works as of April 2021.
