Mechanical slaughter of animals, it should be noted, is a matter that
pertains to ijtihād and there is bound to be difference of opinion in this.
Personally, I do not see any harm in this. Taking the takbīr once at the
start suffices for the whole lot since the same machine is going to actually
slaughter all the chickens. Defective machines obviously must not be used
and it should be made sure that they are properly slaughtering the animal.
also remember that the Qur’ān prohibits ‘poured forth blood’ (damun masfūh).
Blood which is left or held back in veins and arteries after the slaughter
is not prohibited. The blood that slowly oozes out while cooking is the one
which is left in the arteries. So this cannot be objected to.