My 4 girls are 19 weeks old. I hope to have my first eggs within the next several weeks. I still have most of a large bag of grower feed. Will it hurt to keep them on this while offering oyster shell once they start laying (until I use up my grower feed), or should I go ahead and switch?
It is absolutely fine to go ahead and finish up the grower feed you have and switch to layer next bag.
It's good to have a little left over with the first feed when switching to another. I use the last bits to gradually switch over. I'll use 3/4 original and 1/4 new for a few days then 1/2 and 1/2 for a few more and 1/4 original with 3/4 new until the original feed is gone. I do that with all my animals to prevent any kind of upsets with switching.