The breakdown is something like this:
Starter: 22-26% protein
Starter/Grower: 18-20% protein
Layer: 16-18% protein, w/ additional calcium
NOTE: DO NOT give layer feed to chicks. The extra calcium can cause them problems.
I'm generalizing here, as there is variety in the market. I buy a local feed from the mill which is different than Purina's product, which is different than Dumour's etc. There is certainly some textbook "perfect value," but just like with humans the textbook optimum is just that - a textbook value. There may be some legal requirement that producers have to adhere to, as well - but I doubt it. If so, I'd sure like to see it.
These numbers serve to illustrate the greater point about protein needs through the various stages of the chickens life.
Stick with a good ration, with a protein content within a point or two of these numbers and you can relax a little on that score.
'About medication in starter feed. It's there to combat the spread of coccidiosis, in the main. This parasitic disease can decimate a flock and chicks are highly susceptible to it. "Nip it in the bud," is the philosophy behind it's presence in chicks starter.
Is it absolutely neccessary? Maybe, maybe not.
But, what are you gonna serve by not offering it - holding your little chickies to some high-minded "organic" ideal, perhaps?
That's your choice, of course, but they know nothing of such things. Why not give them the "Better Living Through Chemistry" advantages YOU enjoy in everyday life?
It's become a standard, industry wide, for good reason and most starter feeds I'm familiar with include it.
RELAX is possibly the best advice you can get on this whole issue. After all the learnin', cussin' and discussin' is done, your choices have pretty much been taken care of for you:
Buy a good starter feed from a reputable maker and feed that, phasing in the next level at aout 1-2 months. After 4-5 months phase over to layer feed and dont look back until next season.