Translations:Pferd & Pony – Mein Pferdehof/129/en

A mare's pregnancy goes on even if she's sold to the breeder. If you re-buy her 20 rounds after she got pregnant, she will give birth to a foal the next round which is already ~11 rounds of age. After another round, the game checks its age and it grows up immediately. This way, you save time and resources by having “external“ breeding mares, and you don't have to wait for your yearling to grow up before you can ride it (usually, growing up takes longer than the exercise stat decays to an uncomfortable point). This way, you only wait until it actually gains enough strength before you can start training. Plus, if it's a mare, you can add her to your breeding program right away.