I might be way off here...but i usualyl have 300-500 baby bps every year and i start them off on Small adult mice out of the egg...and by 3-4 months depending on the particualr animal they are usually on multiple mice or rat crawlers at that age...and at around the 200-250 gram mark i move them up to rat weanlings...almost 10 years of that and i never knew i was doing it wrong LOL