Good Morning S.! Oh Happy Valentines Day to you and your Silly little guy. OK First question, Where is it written in stone a child has to be using a sippy cup by age 1? Probably in a Dr.'s dusty How to book? :)) No seriously S. there isn't any reason at all ( except the EXPERTS) say this is the Thing to do.
I let our Boys have their bottles Until They gave them up themselves. First one threw it away at 19 mon. Our Second had his until he was a little over 2, then he did the same.
With our gr son's Corbin liked to drink from my glass sometimes, had a bottle most of the time until after age 2. He still likes warm milk in the morning with his breakfast with a covered sippy. Zane doesn't care what he uses...lol He might use a sippy of some kind during the day, nap time and bed time he has his bottle he is 16 mon.
There is no reason what so ever to take a bottle away from a baby at age One. It helps them self soothe, its a comfort thing. So why don't ya follow your heart, you know him better then any of us here and better then your Dr. also.
Now if he wants to take it for Show N Tell in Preschool, ya might need to talk that over. :))
God Bless, As for the different types of formula's or milk products, I have no idea. My brother was on Soybean milk for a very long time. He is 54...lol
K. Nana of 5