I saw some chicken eat chicken bone

I saw some three month age chicken eat the chicken bone. chicken is omnivore which means they can eat both meat and vegetable. They can eat insect, worm, mite, and they can eat grass, paddy, wheat,flour and so on. I am worried the chicken will gonna mad after eat chicken bone. I hear the mad cow disease occur because the cow eat the meat cow. Supposedly the chicken owner house the chicken so they will not eat the chicken bone. The chicken bone must be bad for the chicken. They can feed chicken with common chicken food such as grain, seed, grass, and insect. Read Also The chicken breed that right for you Japanese Bantam