My experience is with the Murray Grey breed, so I have to speak from that point of view.
One of our best cows was out of a first calf Murray Grey heifer and a 10 year old Murray Grey bull. The calf had a 60# birthweight.
The birthweight is almost all in the genetics of the bull and the cow. The birthweight of the calf sired by a particular bull won't get bigger as the bull ages.
As for the size of the bull, if his conformation is good & he is healthy with good feet, he should have good balance when breeding a heifer or cow, no matter what his age. As a Murray Grey breeder friend says, "The bull should be able to pick apples out of a tree."
> Too heavy to get up on top to
> service the cow? Too heavy (too
> big) for the cow to be safe under
> him...? The last bull dad had
> started throwing calves that were
> over a hundred pounds... is that
> possible???? the calves just kept
> getting bigger.... but, basically
> the first question is the main