This is often even done without it being intended as well. If you think about a commercial chick business where eggs are incubated artificially and NEVER hatched naturally, those hens with the least brooding instinct will have far more off spring because they are not taking several months off of laying each year to try to brood. Eggs are simply collected and placed in an incubator and those hens without broodiness are more likely to pass on their genetics.
do a search in the block above for 'how to break a broody'.... it is a frequently covered subject and there are many methods, not every method works for every hen and you may have to try a couple to get one that works. The subject has been covered in this thread at least 2 or 3 times in the past 4-6 weeks, if you do a search this thread' (from the choices below the last thread entry) for 'breaking a broody' you should get your answer.
Hens can have fertilized eggs for 3 to 4 weeks after their last exposure to a rooster. So even if you removed a hen from any rooster contact on the first of the month you may still have eggs laid by that hen on the 25th of the month which were fertilized by that rooster. To ensure clean genetic matings people will keep a hen isolated from all roosters except their preferred mate for her for a month before they will begin to collect hatching eggs and be able to be certain that the intended rooster is indeed the daddy.
