Yes,
It's a hormone used to make them grow faster. It's name is melatonin, and you can buy it over the counter as a sleep aid. However, I don't consider it entirely safe, as no hormone or drug should be considered safe.
There are hormones in beef as well, and genetically altered foods are everywhere now. We got killer bees thanks to genetically altering bees, and now we play with fire again. It's best not to worry about the stuff, as that is what usually gets us. 99% of illness is believed to be psychosomatic, or stress induced.