Yeah, that combined Starter/Grower should be around 20% protein, which is the same as Flock Raiser. The other components are close enough that there is no significant difference. You can feed either one with oyster shell on the side. Especially for growing chicks, I would not mix oyster shell in with the feed.
If the chicks are over 4 weeks old, you can use Grower of you want. That works well for chicks that will become part of a laying flock, not real well if you have meaties. It has the same percent protein as Layer, just without the extra calcium that can be harmful for growing chicks.
If the chicks are over 4 weeks old, you can use Grower of you want. That works well for chicks that will become part of a laying flock, not real well if you have meaties. It has the same percent protein as Layer, just without the extra calcium that can be harmful for growing chicks.