You will have to use the mouse for this game.
Take a good care of this mamma horse and try to fulfil her needs so she could have an easy pregnancy and give birth in a safe environment. This horse game will put you to supervise her birth giving and once her medical condition is good enough you will assist her with it. Then you will have to look after the baby horse and make sure he is feed and washed out. Dress up both of them and have a lovely time.