According to a Rudolph Steiner's conference (1923) i just read, if a vegetarian animal eats meat he gets mad. (I'll try to find it in english for
the technical details.) As long as rendering plants will exists mad cow disease will strike.
NY Times (Britain Mad cows) : ''Nevertheless, the agency wants to restrict the little-known agricultural practice that lies behind the problem in
Britain: the use of rendered animal tissue in animal feed. In the process, they are drawing new attention to rendering -- the ancient but
seldom-discussed practice rendering plants who are boiling down and making feed meal and other products out of slaughterhouse and restaurant scraps,
dead farm animals, road kill, cats and dogs euthanized in some animal shelters''----- and lab animals (i interviewed the director of guelph
university couple years ago for an article about a chicken farm which feeded ''by mistake'' their birds with transgenic pigs (from Guelph labs)
and he told me that many lab animals were sent to the rendering plants.)
Cows eating meat = mad cows

Cows are vegetarian animals stupid farmers.
Mad cow outbreak may have been caused by animal rendering plants