Solids are recommended at 6 months by most Australian guidelines. The allergy council is now suggesting beginning between 4 and 6 months (purely based on allergy reasons) but definitely not before 4. I don't agree with introducing solids soon and definitely not as a replacement of a milk feed at this age but obviously it isn't my choice, I would suggest looking into all the advice and reasons why they are as they are first though.

If he seems hungry could you offer more bottles or more per bottle?