[demosthenes the elder]

well, THAT is gross.
I dunno how "cruel" and "barbarous" it may have been.
The chickens were marked for death, no matter what.
It seems to me the farmers chose an effective expedient method for mass slaughter.
That many chickens suggests a big-ass chipper, not one of the dinky ones you can rent. One that is top-loaded from a hopper, with a down-angled chute, with fittings for bags at the bottom. They are also FAST. Too fast for significant levels of pain to be reported to a creature's brain before the brain itself is mulched.
So, again, dunno about this "cruel" stuff.
Certainly paints a nauseating picture, though. ICK.

[Eaker]

a big-ass chipper

Would that be the Jennifer Lopez model????