My DD fed from both sides, but my right was always her fave. It was the side that she fell asleep on better too. Recently she told me that the left has "cow milk" in it, but the right has "mummy milk". Now, she only feeds once a day, and she always go to the right.

In saying this, both sides have nourished 2 children and the milk from both is awesome quality

I haven't been a big expresser, but have noticed that my milk can look quite different on different days. More 'cream', different colours etc. It's never worried me, cos when baby feeds at the breast i can't see what the milk is like and they never have a problem with it.