I have a 1 year old female GSD who is currently around 65-70lbs. Her mom was ~75+, and her dad was a small horse.
She is currently getting ~2.5-2.75 lbs of food once a day. Her current menu consists of some mix of; turkey neck, whole chicken leg or thigh, turkey leg, duck wings, blueridge organ mix, blueridge tripe mix, whole sardines (not as much, she's getting picky about them), and a fresh raw egg every other day or so. Sometime I mix in fresh beef liver as well.
At one point I had her up to ~3 lbs a day, and she started getting picky and only eating her favorite items. I dropped down to 2 lbs, and she started going to the fridge all the time asking for food. So I slowly worked her back up to what she is eating right now.
I was told by the breeder to keep her "thin" until she's finished growing (~1.5 yrs), to help avoid hip problems. The guideline for "thin" is kind of vague though, I just want to make sure I'm not starving the poor thing. She feels slightly ribby right now, but isn't begging for food constantly.
She's very active, always wants to go outside and play, and has a large backyard that she'll tear up and down chasing pine cones if given half a chance, so plenty of energy.