Exactly, and I am a firm believer in performance in cattle being completely different if the feed is changed.  As well, some of the drugs to get cows to cycle I think leads to lower fertility issues as the genetics to some degree become dependant on the drug.  Instead of weeding out the fertility problems those cows stay in the herd.  Mainly the feed situation is why we started retaining our own bulls, then we know what works with our herd.