The FDA just banned brains, skulls, and spinal cord from being used in cosmetics and dietary supplements. However they decided to delay banning those things from cattle feed for another two years. The article goes on to state "Also the FDA hopes to adopt a ban on cattle blood and poultry litter in cattle feed later this year."
As of right now it is okay, indeed standard practice, to feed blood from cattle, pig parts, and chicken manure to cattle. Such wonderful practices are why I eat organic meats.