Richard you are right about the eared cattle. I had Santa Gertudis bull years ago. Calves came out like wet noodles and grew like crazy.
Dun, don't for a minute doubt your figures. But I still can't wrap my head around the fact that if you took those 65lb heifer calves, bred them to a low birthweight bull, and did it for several generations that even with closely watched genetics, your weaning weights would go down. They would soon be having those 50 lb birthweights, and those calves can't wean as big as the original great-grandma's calves were, even tho' in their comtempory group, they were within 10 lbs of each other. I just think to get the weaning weights up, you gotta' keep the birthweights up. Otherwise, lets all go to 30lb calves. JMHO gs