Poultry Additives Question...

Well, actually it concerns eggs. Where I live there's a lot of people who are very "naturalist" and don't like additives to food, and lately they've started to go on about people giving chickens stimulants to produce more eggs. Because of this the schools have started assigning students to make papers on the substance.

I was wondering if anyone couild give me information on a chemical given to poultry that could increase the amount of eggs that the chicken would lay and what might be used to indicate its presence.

Thanks a lot for any help.