That's not why I asked, I have mature hens but would like to start hatching from my Wheaten Marans pullets also. Thank you for breaking that all down.I have never heard a specific number of grams or ounces just when it is in the normal size range for the breed. One issue I have heard with breeding from pullets is you don’t have any information on the long term health of the bird your breeding. Like if you only hatch from pullets then a couple years from now you discover that your birds all have been issues getting egg bound and prolapsing at two years old or they all have hip issues when the get older these can be a very hard problem to correct after you have been breeding from them the whole time.
I’m not saying don’t try it but don’t invest everything into the young pullets just because you think they are an improvement over the older birds in the flock.