Do keep in mind that horses are difficult animals to feed compared to most livestock. And even more difficult to breed if they don't live in a large group, and you don't understand the process of artificially inseminating them. Horses are finicky about that. Just owning a stallion and mare is usually not good enough.

In areas with a lot of suitable pasture horses can be common, while in densely populated areas with no natural grass they are a luxury imported from abroad, difficult to keep alive over the winter.

Research on age and gender distributions of horse bones collections in the Roman empire and China shows that these cultures mostly imported their horses and breeding was relatively rare. Steppe peoples on the other hand ate and sold young stallions in great quantities.

In the relatively wet plains of Northern and Eastern Europe plowing with horses was common in the middle ages. In the drier landscapes of the mediteranean oxes were used for that purpose.