Let me emphasize on the fact that breast milk is the best feed for a baby upto 6 months of age. Beyond that, the baby needs a mashed version of adult diet low on spices, introduced step by step. Milk becomes an optional component at this age if other sources of nutrients are included in diet. Cow or buffalo milk has high protein content and hence is difficult for a baby to digest. Most formula milks are cow milk based and although they are not directly harmful and may be given but I would prefer home made semi solids made from boiling rice and pulses along with vegetables and giving it after mashing it. You are doing the right thing by giving Khichdi, Ragi and pulp of fresh fruits. Most of these would be more nutritive than the available formula and so I would not speak in favour of formula like NAN or buffalo milk.