[0] Now there can be a very complex discussion about this. I'm not saying slaughtering is unproblematic. I'm not saying you couldn't try to make a similar point for humans to which I would also have replies why that's a different matter. I'm just making the point for this specific purpose of comparing here.
I think it's likely that even the most terribly mistreated lab animal has a better quality of life and death than the average US foodstock chicken.
I've been involved in atudies where we cut the heart out of sheep and then implanted a pump to replace it. One animal had the pump strapped to its back. The animal bumped up against its pen one day and broke one of the 1/2" tubes free and the pump (artificial heart) sprayed blood all over the pen and the animal bled out. We discovered it in the morning.
I'd rather do just about anything than that. Worst death imaginable.
I'd love to see some sources that support such a strong claim. Otherwise, it just comes off as bait for argument.