I have two kids with PKU. I nursed both of them until they didn't want to anymore (my son @ 4 months, daughter @ 6 months). The feeding schedule was similar to two bottle feedings with formula for every one breast feeding. Eventually they wanted the bottle rather than nursing because it is easier. After that I would add regular baby formula to their PKU formula (their dietian figured out how much of each) and bottle fed them. I didn't start baby foods until they showed interest in eating it. Hope this is helpful.