I have a trio of bearded buff silkies in a breeding pen right now. Currently both hens are laying. I put some blue food dye in the vent of one of the hens, and around the vent. The other hen I used yellow. When they lay the eggs, there is dye on the eggs, so I can keep track of which hen laid which egg. Thus seperating them before they hatch so I know which hen produced which babies. The dye also lasts for about 3-4 days. Just make sure to put it in and around the vent. LOL. I cant believe im actually putting dye into a hens vent.