Glad I found this thread! My son's 19th birthday cake was a Sam's Club triple chocolate fudge "death by chocolate" type with an insane amount of fudgey frosting and flaked dark chocolate on the edges. After the party I scraped off the plates in the "for the chickens" scraps bucket, then thought seriously about the chocolate.
If it had been MILK chocolate I don't think I'dve worried too much, but it's dark chocolate, and not just a little bit.... maybe two cups or more of dark chocolate buttercream with all that flaked chocolate besides.
I've occasionally given the girls (and my dogs) minute licks of chocolate ice cream or an occasional Oreo cookie with no problems. Oreos have more food coloring in them than chocolate anyways. But there's no way I'll give them any of my stash of 60% or 70% cacao dark chocolate bars!!
I agree; it's the heavy concentration of theobromine in darker kinds of chocolate that's the danger, and why I chose to put the frosting in the compost pile rather than in the chicken run.
However, they thoroughly enjoyed the bits of leftover cranberry sauce, the turkey carcass, and the leftover sweet potato mash!