Let me correct myself. The starter/grower is recommended for up to 10 weeks when you switch them to grower/finisher until 18 weeks (or laying). Forgot that transition.You only need grit if you are feeding them treats. If you are just feeding them the starter crumbles you don't need the grit. If you give them other treats, then yes, you'll need the grit. I just sprinkle some grit (I get mine from TSC..basic Chick grit) on the floor of the pen and they dig and peck for it. They should be on the starter/grower crumbles until you switch them to layer or flock food. (Usually about 16-18 weeks). If you look at the back of the Dumor starter crumbles (TSC sells) it'll show you a chart to help decide when to change to what.
Just make sure their regular food is what they are getting the most of and not other foods or treats. The starter crumbles have what they need to grow.
