More experienced keepers will respond with more detailed information, I'm sure - but a sulcata's need for the appropriate amount of protein is supplied through the plants they eat - not meat, dog or cat food. Robyn (Crazy1) did an extensive listing of plants recently that might be helpful to you. Also I rely on www.africantortoise.com which expressly focuses on sulcatas and leopards, including diet info. Hope that helps
I don't think they need much protein at all. In fact, you have to limit how much protein you feed. For example, you want to feed the most low protein hay, not alfalfa. I think it's an old school of thought that you need to feed beans and such for protein to a tort. Look what they eat in the wild--weeds, grasses, etc. Those are all low in protein, and what you'd want to replicate in captivity. Who told you they need protein?
All foods have protein in them, and the type of foods that a sulcata requires,weeds and grasses, also have protein in them. Its the type of protein that should concern you. They DON'T need animal protein, and too much alfalfa, because of the protein, is harmful to their kidneys. So just stick with a diet of weeds and grasses, and you can't go wrong. How big is your sulcata? Babies have a hard time with weeds and grasses, so we substitute Spring Mix with a bit of grass and weeds sprinkled on top.