Well, I certainly don't want to argue with dlhunicorn, whose vast information knowledge has helped us through many chicken crises, however from what I have read many times, this IS still allowed: beef by-products are made into chicken feed, then the chicken by=products (including "litter") is made into cow feed.
Here are a few quotes: from the CA dept of Ag site:
http://www.cdfa.ca.gov/ahfss/Meat_and_Poultry_Inspection/By_Products.html
Beef By-Products>From Fats & Fatty - Acids >Chicken Feed
From May 2007
http://network.bestfriends.org/dc/news/14673.html
What Exactly Do Hogs, Cattle and Chicken Eat?.....
...but additives like blood, manure and even unborn calf carcasses are allowed under state or federal rules. Meat byproducts are also common; those are the parts left over after pigs, cattle or other animals are slaughtered and the meat removed for human consumption. The byproducts include the lungs, brain, spleen and internal organs along with bone.
2004 (ok, its old) LA Times:
For instance: When feed containing rendered cattle is given to poultry, some of it scatters on the floor as the birds peck at it. The floor is also thick with excrement, feathers, dirt and bits of straw. Rather than throw all that waste away, farmers sweep it up and recycle it -- by selling it as cattle feed.
The FDA allows that practice, which is most common in the big chicken-producing states of the Southeast.
However, this from AGNews 2004: they must NOT have passed these regulations (banning feeding chicken litter to cows) because I found plenty more up-to-date mentions of the practice...
http://agnewsarchive.tamu.edu/dailynews/stories/ANSC/Feb2304a.htm
I could not find any mention of newer laws banning either beef by-products in poultry feed nor poultry litter & by-products in cattle feed.
personally, I'm not interested in risking it either way. I also don't want to eat stale candy bars, stale chewing gum in its aluminum wrappers, manure, and heat-treated municipal garbage, all of which are also in cattle feed. I read a bunch of articles which made a big deal out of how EFFICIENT it was to turn GARBAGE into protein to feed humans... and OK maybe that's true, but I DO NOT want to eat it! And I won't feed it to my family.
It's just not that hard to find a good alternative, and in my area, as consumer demand is growing, its becoming easier and cheaper to find good, locally grown organic alternatives. Hooray!!! I get to eat better, healthier, tastier food, AND support small farmers in my community. How cool is that?!?
Stacey