This thread's already been derailed so hard that it's landed on another continental track altogether (including by me, for which I apologize), but allow me one last rebuttal:
Cows are herbivores so yes putting meat in their feed is a bad idea. Chickens however are optimistic omnivores that eat anything they can get their beaks on, which most certainly includes meat. At any rate, mine only get it as an occasional treat as they do with other type of food (fruits, veggies, greens, grass, bugs, ect.) beyond their staple formulated pellet food.