2.  Animal residues that remain after rendering fat in a slaughterhouse, used for fertilizer or feed.
and 
3. (Life Sciences & Allied Applications / Agriculture) Agriculture
a.  fertilizer consisting of the dried and ground residues of animal carcasses
b.  a protein supplement feed for livestock
So um.....it sounds like a low-end, low-cost way of upping the protein content of the feed. Feather eating is usually the result of protein deficiency.
Feather picking (without eating the feathers) is usually the result of overcrowding and boredom. Best to figure out which is the problem 
However, upping the protein of the feed isn't hard. MOST people on this forum usually use gamebird food or chicken grower food.
If you are feeding a lot of corn or scratch treats, cut all that out. If you want to feed treats use black oil sunflower seeds instead of scratch.