My 3 girls are going to be 19 weeks this week and I am going to buy a bag of layer crumble and mix the last 1/4 part of my grower bag on the top to move them over. From what I have read and seen here there is no hard and fast age to stop and start. It all seems to be kind of gray mixed with personal preference, although there are obvious thoughts about age and protein mixture, like puppy food for puppies, adult food ... and so on.
I have a mixed flock of roos, hens and pullets. I feed starter/grower still with oyster shell on the side.
My roos and laying hens are 22 weeks old, the pullets, 12 weeks old.
My eggs are very hard shelled, the hens are eating the oyster shell when they need it. I will switch them all over to layer
feed when my 3 EE;s start to lay. I have heard Flockraiser is better when dealing with roos, with oyster shell on the side
for the layers.
I figure my roos will be ok with layer feed...I will mix it with whatever starter/grower I have left to transition them over.
Hope that helps, it's just my way of doing it, others do it differently.
As one person said here, and I think put it perfectly....layer feed is for when they start to lay. So, depending on when you get your first egg, switch then. I have 5 BSL that are now 23 weeks and 3 Americaunas that are just 20 weeks. Approx 3 weeks ago, one of my BSL's started to lay, so I bought layer feed then. I have been alternating in the bin a layer of grower/finisher then layer of layer feed, then grower then layer, etc. until I use the rest of my grower feed. Then everyone will get only layer. Plus, I didn't want to waste the grower food since I had over half of a 50 lb bag. I also do have some grit and some oyster shell that they can get when they want. I will put some in a seperate bowl a couple times a week or throw some grit on the run floor because they like to scratch at it and peck at it.
So, basically, when they start to lay, then get the layer feed. Don't worry about their age too much. They will lay when they are mature and ready.