ואם לא תפדה וערפתו
שמות יג יג
If one doesn't redeem a first born donkey, then he should kill it.
With a hatchet
It is forbidden to derive benefit from a first born donkey who has not been redeemed, whether or not it is killed. It is even forbidden to derive benefit from the carcass.
Males and females. Yisraelim but not Kohanim, Leviim .
In the 1st Perek of Masechta Bechoros
Hashem decreed that if you don’t redeem it as one is supposed to, that one may not derive benefit from it. Rather he must kill it.
The first choice is to redeem it. This Mitzva is second choice.