>2.  Why is it that some modern cows can only survive on concentrated feeds?


What cattle can only survive on concentrated feeds? The most specialized
breed I know is the Holstien, which can survive fine on roughage, it just
won't produce commercial quantities of milk. As to very specialized beef
breeds, like the Hereford, they are also fine on grass. In fact the cows,
bulls and calves on the western ranches live a mostly wild life, unless the
environment gets rough.

The breeds aren't really adapted to a heavy grain ration as regards their
health, it is a commercial decision. It is cheaper to replace burned out
cows every few years, than to accept the low milk yields that would follow
from a ration more heavily dependent on grass.

Ask a dairyman how long his cows last, compared to his father and
grandfather's.

Michael