70 day old chickens - when/how do Introduce grit?

[Mouthwash]

Right now they're still eating the 50lb bag of DuMor 20% chick starter but are gonna KO it soon, probably in a week or 2. We've also started giving them some treats such as bananas, spinach, finely diced apples etc. Do I need to introduce grit into their diet already because of the treats/whatever they find on the ground in their run?? After this bag or chick starter is empty, can I switch to egg laying mix for them even though it's still a couple months before they lay?

Their run is small and don't wanna waste real-estate on a bucket of grit, and I just sprinkle it on the ground?

The run will consist of a few inches of bark chips, so they will not be free ranging regularly.

 

[KarynVA]

You can introduce grit by sprinkling some on the ground in their run or put a small cup of grit where they can reach it. I used a metal cup with a bracket that hooks onto the hardware cloth and fill that with grit as needed.

I would not endorse feeding them layer feed too soon before they are expected to lay. If you are still in the bag of chick starter when it gets closer to laying time, you can start mixing layer food into it until it is all used up and then straight layer feed as they start laying.

 

[Stravager]

If you're introducing stuff like greens then yes, they need grit. You can throw it on the ground and they'll find it (but that's easier to do on grass or gravel, not sure about bark chips) or do what KarynVA said and use a small cup or something wired to the fence, however if they aren't going to be using the run on a regular basis you might want the grit to be somewhere where they can always access it.
Excess calcium and protein can cause a multitude of health issues in the long run. Ideally you would have already switched them onto a grower feed (somewhere around 16-18 percent protein) after the first 45 days, but I would start doing that now. You should still have roughly about 56 days before they lay start laying so that should be plenty of time to get through a bag.

 

[FunClucks]

You can feed starter/grower and never change over to layer feed at all. Or change later after everyone is laying. Put separate small containers of grit and oyster shell/calcium rocks in the run (you can attach them to the side of the run, and they won't take up much room), or you can make obstacles for the chickens to climb and put them on top of that.

The grit is needed whenever they're on dirt or shavings IMO, basically whenever they eat anything but commercial chicken food - mine are always eating something off the ground or the random insect or shavings piece.

Calcium rocks/oyster shell - keep those in the run at all times - the chickens will eat as much as they need to meet their calcium requirements. The layers will eat it, the non laying hens, chicks, roosters, will not. Same goes for grit - the chickens know how much they need and what size grit to eat.