First degree of abstraction: the common chicken, domesticated over millennia to select for edibility, docility, and big, yummy eggs.
Second degree of abstraction: a roasted chicken, delivering on the implicit promise in its breeding. Now suitable for consumption.
Third degree of abstraction: the drumstick, separated from the rest of the roasted chicken's body and reified as a meal or a product in itself. Instantly identifiable and even synecdochal, the part of the chicken standing for the whole.
Fifth degree of abstraction: "drumstix"-shaped edible dog treats, presumably made with a variety of ingredients, including a few derived from chickens. Visually, the iconography of the drumstick has been flattened and miniaturized. The shape says "chicken" to humans, who do the buying, while the smell probably says something similar to dogs, who do the eating.
Final degree of abstraction: flat, miniaturized, drumstick-shaped, reconstituted chicken-plus-other-stuff sold for human consumption. The dematerialized signifier is reunited with its original signified, albeit with the entire genealogy of abstraction still compressed between the two. The entire history of consumer culture writ small. Yum!