YOU SAID:
i have one cat and i use to have a ferret
INTO JAPANESE
私は猫を1匹飼っていて、フェレットを飼っていました
BACK INTO ENGLISH
I had a cat and a ferret
INTO JAPANESE
私は猫とフェレットを飼っていました
BACK INTO ENGLISH
I had a cat and a ferret
That didn't even make that much sense in English.