My digestive system very simply cannot handle ground meat from grain fed cattle. I'm not sure why only the ground meat affects me but I finally gave up eating hamburger, including organic because of the digestive issues. I recently tried some grass fed, grass finished ground beef and much to my surprise I was able to enjoy it without the digestive distress. Who knows why. I certainly don't, but grass fed/finished beef is $4/pound cheaper than the bison or elk I was buying to use instead of hamburger, so I am happy.
Z