Good question. I’ll answer another one that might help you.
It takes about 25 hours for an egg to make it through the hen’s internal egg laying factory. It can only be fertilized in the very first few minutes of that journey. So if a mating takes place on a Friday, Friday’s egg is obviously not fertile. Saturday’s egg might or might not be fertile, depending on time of day the mating took place and the egg started its journey. I would not count on it. Sunday’s egg will be fertile. Note this is after a mating. A rooster does not mate with every hen in his flock every day, though it seems he tries.
Most people use that a hen will probably stay fertile for two weeks after a mating. You’re dealing with living animals so you can’t always be certain, but the two weeks works most of the time.
Now to your question. A hen can stay fertile for over three weeks after a mating. Most don’t and many people use a 3 week period of waiting but some use a 4 week period to be absolutely sure.
There is something else at work here too. After a mating the hen fluffs up and shakes. This gets the sperm in a tube near where the egg starts its journey. This tube works on a last in – first out basis. This means that the last rooster to fertilize the hen will most likely be the father of the chick. I don’t know how often a mating has to take place to keep his sperm on top, but in a breeding pen with just a few hens he will probably take care of that.
So to be absolutely sure, wait four weeks. To be pretty darn sure, wait three weeks. To be fairly sure, give her a few days to empty out that tube a bit and go for it.
