Jan, I have also heard about formula having a soporific effect. Peter Hartmann talks about the casein being broken down into caseinomorphins, which have a morphine-like effect. Hence the advertising claim that a certain casein-dominant formula is good for "hard-to-settle" babies. In the calf, this is a desirable effect as it allows the mother cow to go off and graze in peace, while her calf lies quiet and still in the grass - less likely to be spotted by predators. Something like this I think. Food for thought, eh? Joy Anderson IBCLC Perth, Western Australia