YOU SAID:

can't straw in the horse's back

INTO JAPANESE

馬の背中に藁を入れることはできない

BACK INTO ENGLISH

You can't put straw on a horse's back

INTO JAPANESE

馬の背中に藁を敷くことはできない

BACK INTO ENGLISH

You can't put straw on your horse's back

INTO JAPANESE

馬の背中に藁を敷いてはいけない

BACK INTO ENGLISH

Don't put straw on your horse's back

INTO JAPANESE

馬の背中に藁を敷いてはいけない

BACK INTO ENGLISH

Don't put straw on your horse's back