I started my BJGs immediately on a little pinch of coarse corn grits mixed with a pinch of sand. They like to scratch and peck right off the bat, and the grits give them something tasty, while the fine sand goes right to their gizzards. At first they got about 1/2 tsp per day, but it was a start and we worked up from there. By week 2 they were out of the brooder and into the pen and getting yogurt, mealworms, a little chick scratch and a little bit of wild finch food because it has very tiny seeds; we also installed a sandbox in the pen. Week 3 we introduced spinach and rolled oats.
When offering treats keep a couple of things in mind:
* Keep the size of the treat appropriate to the size of the chick eating it. A week old chick cannot handle chick scratch because the chunks are too big. Try fine corn grits at first and work up to larger sized pieces.
* Don't offer too many treats. Their main nutrition should always be from their starter food. A good rule of thumb for treats is no more than 5% of their total nutrition should come from treats, and the total treats you offer should be consumed in 10 minutes or less.
* In order to properly digest anything other than chick rations, the chicks
must have a source of grit. Fine sand works perfectly, and the chickens will consume as much of it as they need.
If you keep those three things in mind, you generally will not go wrong. The chicks know what to do, but it is up to you to give them what they need.