Mine need to be returned then. I have specific hens that will take adult mice, even in my free ranging flock. They'll all gobble down pinkies when I find a nest, but fuzzies and older are ignored by most.
My guess is the preservatives in store meat? I give kine raw meat as treats though
I had a pullet that just gobbled down tomato leaves. Didn't care about the fruit, but she would not stop plucking leaves off the plant whenever she had the chance
Apple seeds are fine too in small amounts. When I give a bird(s) apples, they usually gobble down a couple of the seeds. Just like with people, it takes more than you'd think to get poisoned