A lot of people get confused on all this, mainly because it is so simple that many different things work. There are very few rules to feeding your chickens.
First, do not feed growing chicks Layer. There are a lot of other types of feed out there, but the important difference in any of them and Layer is that Layer has excess calcium in it for the egg shells. There are studies out there that show that the amount of calcium in Layer can harm growing chicks. So rule #1. Do not feed Layer to growing chicks.
Oyster shell and egg shells are primarily calcium. A common way to feed a mixed age flock of chickens where some are laying eggs and need the extra calcium and some are growing and should not have the extra calcium is to offer it on the side, not mixed with the regular feed. They seem to know instinctively if they need it or not. The ones that need it eat it. The ones that don’t won’t eat enough to harm themselves. You can buy a bag of oyster shell fairly cheaply at the feed store. Usually a small bag goes a long way.
The processed chicken feed has been ground up enough that you do not need to provide grit if the processed chicken feed is all they are eating. But they need grit in their gizzard to help them grind up about anything else. Yogurt of course is OK, but don’t feed any grains, green plants, hard shelled bugs, much of anything else without first giving them grit. That’s rule #2,
That’s it for the rules. Pretty simple, Huh?
All you need to give the chickens for good eggs is the feed. It is formulated to contain all the protein, fats, carbohydrates, vitamins, minerals, fiber, amino acids and all that they “need”. Many of us go beyond that. We might allow our chickens to forage for grass and weeds, grass seeds and weed seeds, and all kinds of creepy crawlies. Or we might give them extra grain, greens, or creepy crawlies. If they forage they’ll balance it out themselves but if you are feeding them this other stuff, it’s best to not give them too much of any one thing. The basic feed is a balanced diet. Treat the other stuff as a dessert, nice to have but it should not be a major portion of their diet. Just feed it in moderation, not excess.
The normal recommendation as to when to switch to Layer is when you see the first egg or at 20 weeks, whichever is first. They really don’t need it until they are laying eggs so there is no reason to switch until you actually see an egg. What I’d suggest is to keep feeding what you have and offer oyster shell on the side around week 20 or when you see the first egg. Then when that bag runs out you can switch to Layer or keep feeding what you are and count on the oyster shell to provide the extra calcium. Either way works.
