Tarpan x Belgian?

[TofuChild]

What breed is a Tarpan crossed with a Belgian called?

[Scythian]

It doesn't have a breed designation. (Neither do several other useful crosses, like (Arabian x Forest Horse).

If you breed a (Tarpan x Belgian) to a (Belgian x Forest Horse), you may get a Norman Cob.

PS: Sometimes breeding a Belgian with a Forest Horse results in an Ardennais, which is a breed. However, if the foal doesn't have the right build, type, and height for an Ardennais, it will be designated "Belgian x Forest Horse" -- and *that cross*, NOT an Ardennais, is what you use for the attempt at Norman Cob.

It's important to follow the recipes in the Breeds Wiki exactly.

Sometime when an attempt at a breed different from that of the parents fails, the foal is designated "Grade" meaning essentially "the horse has known ancestors, but no breed label". Failed Thoroughbreds and Lipizzaners are Grades. Sometimes, if the ancestry is simpler, the result is Half. Failed Friesian = Half Forest Horse. Failed Hackney = Half Norfolk Trotter.

tl;dr Breeding in this game is complicated, and you don't always get what you want.