I give my son 1-2oz of fennel-aniseed-caraway tea before every feed because otherwise he would drink 10 or 11 oz each feed which is too much for him. He was never constipated and the poo looks the way it should. He is gaining loads of weight, very content and sleeps 9 hours through at night. He is 3,5 months old now...
He doesn't like drinking water, every time I try giving him it, he doesn't breathe when he drinks and gulps in a realy strange way and then gags
My midwife said that tea or water is essential for bottlefed babies because otherwise they get constipated. If they don't like water, just add the 1oz of water additional to the feed so that the milk is a bit thinner. I don't think you should do that with underweight babies though but it works great for constipation.