YOU SAID:

my mom peed in the horse mouth

INTO JAPANESE

私の母は馬の口でおしっこをした

BACK INTO ENGLISH

My mother peed at the horse's mouth.

INTO JAPANESE

母は馬の口でおしっこをしました。

BACK INTO ENGLISH

My mother peed with the horse's mouth.

INTO JAPANESE

母は馬の口でおしっこをしました。

BACK INTO ENGLISH

My mother peed with the horse's mouth.