I used 6807 in the late early ninties, the biggest group of cows I got were D,s(93) models. They were decent uddered cows, fairly easy keeping, one cow in particular tkra 14D, was the easiest fleshing cow I,ve ever had on the place never raised any replacement worthy calves though and came open as a five year old. To be fair though we have been very demanding in regards to fertility with a 48 day breeding season since 1985, but 14D's modest milk and "buxom" condition did not equal fertility. The 6807 feet were a weak point also, front especially. Never was able to raise a bull from 6807 that passed a BSE. Poor semen that was a result of consistently poorly developed testicles specifically under developed epididymal tails, accounting for all the secondary semen defects. Subsequent phone calls to GDAR, DHD, and Hawkeye West general manager back the early nineties confirmed this as a common problem. If you use any bull enough your bound to get the odd good one. I guess 40 straws wasn't enough.