There are places that sell seed mixes for tortoises. I got mine here and they grew really well. Mine was the russian mix, here is one for grazers:
Grazing Tortoise Seed Mix 1/2 lb Free Shipping! USA only grazing tortoise seed mix [] - $14.95 : Zen Cart!, The Art of E-commerce
The Grazing Tortoise Seed Mix is what I use in my pens. It contains: Crimson Clover Red Clover Creeping Red Fescue Turnip Greens Fescue Kentucy Blue Grass Orchard Grass Wheat Grass Oat Grass Rye Grass Barley Grass Chia Chicory Timothy Grass These seeds were picked for their nutritional value...
www.carolinapetsupply.com