There is a lot of debate on here about how dangerous the extra calcium is to growing chicks or even non-laying chickens. A lot of it is opinion, very little is actual fact. I've seen studies that clearly show that if chicks eat Layer and nothing but Layer the mortality rate is higher. That means more chicks die than average. In those studies, they cut chicks open to see what damage is done to internal organs. On nothing but Layer there is internal organ damage. Not all chicks die. Not all chicks have internal organ damage. But if they eat nothing but Layer more chicks die and many have internal damage, some of it permanent.
Now to my opinion. It is not about how much calcium is in one bite. It is about how many total grams of calcium they eat in the entire day and even then it is the average over several days. They are not going to immediately fall over dead if they take one bite, it is a cumulative effect.
If they eat other low calcium food, the effects of the extra calcium in layer are reduced. How much that effect is reduced depends on how much other stuff they eat and how much calcium is in that other stuff. My broody hens usually take their chicks to the feeders first thing in the morning and maybe once more later in the day. The rest of the time they have them out pecking at the ground and on grass. I don't feed Layer at all, the entire flock always gets Grower with oyster shell on the side. Layer probably would not have much, if any, effect on my broody raised chicks while they are with the broody, but I don't know that. After the broody weans them they would probably eat more of the feed, whether Layer or Grower.
Then you have the question about how much the non-laying adults, roosters or hens not laying because of the molt or age, are affected by the excess calcium. There is one study out there that shows eating nothing but Layer can harm roosters. Can, not necessarily will each and every time.
There are so many unknowns about how much extra calcium it takes to affect non-laying chickens and growing chicks and I have little to no control over how much any one chicken eats of the feed I give them. Also, Grower, Starter, or All-Flock has the basic nutrients any of them need for basic health and productivity other than calcium for egg production. To me the simplest solution is to not feed my mixed flock Layer but give the something else and offer oyster shell on the side for those that need the extra calcium for egg shell production.
