Breast milk is so important in the life of a baby. Actually all the vitamins and other nutrients come from the breast milk. That is how important it is. So I would have prefer going for the breast milk more than the formula. I do not know the reason of giving the bay formula. But I hope that it is a good reason. You can goa nd ask your doctor on the best formula milk. On my behalf I have been giving my child breast milk all through. When the bay stopped taking milk I started with porridge. Or other fruits that she could manage at that time. I don’t think if formula milk had=s the same nutrients like that of breast milk. But I hope you cam find more information from a pediatrician. Or if you want to balance both of the. The breast milk should outdo the formula. And do not mx the to together. I am not really sure of the effect. But I just don’t feel if it is the right thing to do. I think that is the reason the child is gassy. Mixing things for a baby is generally not a good idea. It will mess her stomach.