There are many ways to raise Gacha babies. One of the easiest methods is to take advantage of the fact that Gacha babies will pick up anything from the ground, regardless of its own Weight limit. This allows you to dump a lot of meat on the ground, much more than the baby would normally be able to carry with its natural Weight, which the baby will then pick up and keep in its inventory as food. However, this feeding method is wasteful, because Gacha babies will "overeat" even when they aren't actually hungry, and will therefore waste a lot of food. If you decide to feed the baby, you should therefore only feed them via their inventory until they reach Juvenile phase (10.1%+ maturation), after which you should clear their inventory and let them eat from your Troughs instead, since they won't overeat from troughs.