Lots of breeders switch to puppy food.
I would stick with your regular adult food. Switch to 2-3 meals per day. You can add egg, yogurt or cottage cheese, and fresh meat.
Note: if you supplement calcium (yogurt/cottage cheese) continue to do this throughout lactation. Sometimes people supplement calcium with pills during pregnancy and the body does not work so hard to extract the calcium it needs, then once the puppies seem to be doing well, the breeder stops with the calcium, but the puppies requirement increases with every pound they put on, and the bitch can get a calcium deficiency which can be fatal.
Heidi Ho, Odie
Joy-Joy, Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.