>as long the animal is sold per pound weighted before cutting  of >the
carcass,there is economical interest in producing obese >animal.

Non-saleable fat is all waste for the producer.  so much work has gone into
cattle-breeding to 'fix' this problem, eg:

Piedmontese has proven to be the one carcass breed to effectively trim the
fat from a cattle operation.  Today's cattleman cannot afford the expense of
fat, and must recognize the preferences shown by today's "fat conscious"
consumer.  However, eating quality can become a concern with ultra-lean
beef, with the notable exception of Piedmontese-sired beef.
http://www.montanarange.com/history_north_amer.html

ironically they acknowledge very lean meat is almost inedible!

andrew