A common intestinal disease in chicks is Cocci (coxy) or Coccidiosis. As explained in the Merck Veterinarian Manual , it is a "protozoa of the phylum Apicomplexa, family Eimeriidae," and "Coccidia are almost universally present in poultry-raising operations." Even in healthy environments, the chicks may have some Cocci within their digestive system, but when it overloads their digestive tract, then chicks may fail to thrive and stop eating altogether. Unfortunately, if chicks develop Cocci, the use of medicated starter feed is less than helpful, nor useful in these situations, especially when it involves chicks, because they will usually stop eating. Most chicks and mature chickens can build resistance to Cocci parasites in their digestive system over time if they are raised and kept in a healthy environment. Unfortunately, brooding environments can be difficult to keep clean and "Cocci" free, as the birds are typically eating feed that falls on the flo...