I have 7 girls and one juststarted laying 2 weeks ago the rest should be starting anyday now. I keep them in the run because I live close to the road and close to my neighbor and don't want them in their yard so I do not free rnage them. About 3 times a day I pull grass and feed it to them. I keep layer pellets and oyster shell avaliable at all time and feed them scratch once a day and various other treats. My question is how much grass can I feed them without compromising the integrity of the shells on the eggs?