That practice was legal in the US up until 2009 and while that one is now gone, there are plenty of other whacky practices used in its place.

As a replacement the next wacky idea was to feed cows with chicken manure mixed in hay.

The only problem is cows can still be fed to chickens and the cows then eat the chicken crap, so exactly has changed?

http://www.huffingtonpost.com/michael-greger-md/mad-cow-dise...