The issue with leg problems isn't entirely protein related. A study I read showed that increasing the calcium (and phosphorous) content in broiler feed largely prevented. Of course, those are not the cheapest ingredients so it's unlikely feed makers will be adding extra any time soon. So, supplementing bone meal is a great way around the problem. Not that I've ever had it; because I supplement with bone meal.
Regarding coccidiossis. It's with great pain I have to say that all the books you read which state there are ways to avoid it with good management and naturalopathic means are full of fairy tales. I have discuss with great length with the poultry specialist at our Ag University here, it comes down to three facts:
1) If you do not have coccidiossis in your flock, it is because coccidiossis doesn't thrive in your climate. Hot summers and cold winters kill the oocysts. In wet, coastal Washington, it rarely snows and never gets hot. The oocysts prevail in our soils for decades, just waiting to infect the next beast to come along. Pasture rotation is meaningless for coccidiossis, since it isn't winter killed here (as it is east of the Cascades or up in BC).
2) People who claim to eliminate coccidiossis with pasture rotation and probiotics almost universally live in climates where coccidiossis does not thrive. It's a self fulfilling prophecy. I do give mine live culture yogurt, which makes me feel proactive. But there is scant evidence it affects the mortality rate on the chickens, but hey, at least I tried. Again it's a self-fulfilling prophecy.
3) The only true prevention is to allow your birds to die when they get it, then breed the ones who shrugged-off cocci without so much as a hiccup. Accept these losses, get out of the habit of buying day-olds from far away hatcheries, and you will create a very coccidiossis resistant flock in very few generations. Medicated feeds and Allupirinol upset nature's way by allowing weaker birds to survive; which unfortunately then propagate their genes into the breeding pool.
In conclusion, give your birds some tough love.
I was very very upset with my initial loss (I processed 12 cornish x's out of 30); until I realized I was doing better than a lot of people in my area pasturing meat birds. That's when I consulted the University and he put my head on straight for me. I did feel bad like I was a screw-up doing everything wrong; but then I remember the days as a teenager packing chickens from the farms onto 18 wheelers to go off and be slaughtered. Those wretched things had such a miserable existence, that I didn't even eat chicken for over a decade. It makes me proud for what I am doing here, even with initial high mortality, because it beats the alternatives. Buying chicken at Safeway propagates the screwed-up system in which chickens are so poorly valued.
