There are studies out there that show the excess calcium is harmful to young growing chicks. It’s really hard to find studies that show at what age it is safe to give the excess calcium. The closest I can come is a study where they started feeding excess calcium to 16 week old pullets that were going to be a commercial laying flock to see if preloading them with calcium instead of waiting for them to start laying to get excess calcium had any benefit to the early egg shells. The results were kind of inconclusive but not really any benefits.
The study was not to see how the excess calcium affected their internal organs specifically but I infer that since they were willing to up the calcium at that age the excess calcium was not a problem. This was the commercial egg laying industry so I’d guess they have all kinds of tests and studies about this kind of stuff.
That was for chickens that did not get any treats. All their food came from the layer feed. I don’t know if you are feeding any treats or not. If you are, that would cut down on the amount of calcium they are actually eating. The problem is not how much calcium is in one bite, it’s how much total calcium they eat each day, and as was mentioned, over a time period.
I can’t give you any proof, but my personal opinion is that it’s not a big deal, you can go ahead and feed it if you wish. You can get another bag of flock raiser and mix them too if you wish to cut down on the total calcium they get each day though they are likely to either pick out the pellets and leave the crumbles or pick out the crumbles and leave the pellets. I’ve had different flocks do both of those but if you let them get a bit hungry they won’t starve. They’ll eat it all. That might make you feel better and it certainly won’t do any harm. I would not let that bag of Layer get old and stale. It’s too expensive to waste.
