mostly for lactation..
http://www.caninehealthnutrition.com...uirements.html

didn´t read it all...
http://home.att.net/~cusickbook/2.pdf

Weaning
By five weeks after birth, most puppies are showing an interest in their mother’s food. Gradually, the puppies will begin eating more solid food and nursing less. At the same time, the nursing mother will usually begin eating less. Most puppies are completely weaned around 8 weeks after birth. By this time, the mother’s energy requirement is back to normal, and she should be eating her normal pre-pregnancy diet.

http://www.petngarden.com/dogs/dogs57.php

I´ve had puppies... but I´ve never followed the fasting rule I just gradually decrease food intake a bit so no more milk is coming in...and it´s a gradual thing puppies set their own pace....