There is doubt to know if the animal is still alive or not because some of them are not moving anymore after stunning and some are moving but suffered (before the slaughtering).
Q: Is it permissible to stun an animal before slaughtering?
Q: Due to many negative factors, for example, blood clotting, stunning
without any reason is Makrooh (reprehensible). (Shaami vol.6 pg.296; HM
Saeed)
If the animal is wild and uncontrollable, then only will one be excused for
stunning the animal. The sacrifice will be valid only if the animal was
alive at the time of slaughtering after the stunning.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai
FATWA DEPT.