[sh3ph3rd]

I'm not going to claim to actually have a clue on this subject, but in my experience with chickens, all young males produce entirely male or almost entirely male offspring every time. I think it's a natural mechanism to provide a disposable generation to prevent a precocious/premature sire being inundated by his own sons by the time he comes to full maturity. Excessively young males don't seem to produce strong offspring; they're noticeably weakly, smaller, less prime in every way compared to the offspring he'll have later, and it's got nothing to do with the age of the females. I deliberately breed 'young teenage' males to get munchy-only crops, so to speak, as it's a reliable way for me to obtain about 99%-male crops. 

It would make sense that a very young male would produce excessively weakly all-male offspring that are more likely to fail to become breeding males if they do make it to adulthood. I think it's a population and genetic strength control mechanism. If every adolescent male managed to sow his wild oats and the 'oats' were good enough to make it to breeding age in turn, the flocks would be overrun quickly with unproven genes, unlike those of males in their prime who have fought to obtain territory and thus been proven both strong and healthy enough to sire good stock.

But this is poultry I'm talking about, I've not bred sheep yet, only reared orphan lambs. Just a theory, since I notice many species including mammals seem to produce so-called disposable generations of weaker offspring (predominantly male) if the parents are too young, particularly the father.