“Bone meal” and “feather meal” are commodity byproducts of the meat industry. You can find them used in animal feeds and even pet foods.

Moreover, bone meal is also sold as a human nutritional supplement, but curiously under disguised names, e.g. "Calcium Hydroxyapatite" (while bone meal does indeed contain hydroxyapatite, it also contains other minerals and a large amount of proteins), presumably in order to not scare the vegans, who are the main people who need such a nutritional supplement.

While I eat almost only vegan food, I make an exception and I add to some of my food small quantities of such bone meal. However, unlike most people, I read very carefully the small print, so I am aware that this supplement is in fact made from cattle bones, even if its label does not suggest this.