Below is an article which may be of help to you . I also included the web site address which I found it on.
Game bird feeds are available with several types of medications for preventing or treating diseases. The two most common medications added to feeds are coccidiostats and antibiotics.
Coccidiosis is a disease of the digestive tract caused by protozoan organisms called coccidia. It is difficult to control by sanitation practices alone. The best prevention is continuous use of a drug or coccidiostat that reduces coccidia populations. The coccidiostat is usually added to the feed at low levels and fed continuously. Some coccidiostats are given at elevated levels for treating the disease when symptoms appear. Consult a nutritionist or pathologist before increasing the drug level, since some coccidiostats are toxic at elevated levels.
Growing birds are fed rations containing a coccidiostat from hatch until the last week before slaughter. An unmedicated diet is fed during the last week to assure no drug residues remain in the tissues of the birds. This feeding of unmedicated diets before slaughter is recommended when using any dietary drug, regardless of whether drug restriction is required or not.
As birds mature, they develop a resistance to the coccidia organisms if you control exposure. Birds grown for breeder replacements are fed a coccidiostat until about 16 weeks of age. The medicated feed is then replaced with a feed not containing a coccidiostat. Spotty outbreaks of the disease are controlled by including a coccidiostat in drinking water. Two coccidiostats with Food and Drug Administration (FDA) approval for use in quail feeds are monensin sodium (CobanĀ®) and amprolium.
Antibiotics are also added to some feeds to improve performance and maintain healthy birds. When added at low (prophylactic) levels, antibiotics prevent minor diseases and produce faster, more efficient growth. Higher (therapeutic) levels for treating disease outbreaks are usually given in water or injected into the bird. Examples of FDA approved antibiotics for quail diets are bacitracin and penicillin.
This information was found at
http://msucares.com/pubs/publications/p2383.htm