*GRAPHIC PHOTOS* What Killed My Chickens?

[WingItRanch]

Are dogs likely to turn down the chance of my free ranging birds and go for my breeding pen birds instead?

My breeding pens are inside my fenced in ranging area. My layer birds were out and about when the birds in the pens were killed.

Yes. If they weren't panicking when they saw the dogs, the dogs predator drive might not have kicked in. If your breeding pen chickens are less used to seeing new things like dogs, they may have flapped around scared causing the dogs instincts to kick in.