Mating/Pairing question

This is not a good idea, BIOSECURITY. Chickens can be carriers of disease and show no symptoms, meaning her flock could have diseases they are resistant to and the chickens are healthy but your chickens are not resistant so when exposed to a member of her flock your will get sick or vis versa.
Anytime you add a new chicken it is best to do quarantine. There are articles available telling you how to do it.

 

Sperm can remain viable in a hens reproductive tract for up to 3 weeks post mating. Understand that moving birds back and forth between flocks increases the possibility of disease exposure.

 

Here is a good article. You are better off finding your own rooster quarantine then you can breed. https://www.backyardchickens.com/ar...nderestimated-part-of-raising-chickens.67097/

 

You would need to keep your hen separate from your roo's for a while to make sure that she's not likely to lay eggs from your flock, as for how to achieve the mating without causing problems for both flocks I am not sure how you'd go about that. Maybe see if she'd be willing to keep your hen for at least 30 days in quarantine. Then mate and bring your girl back and do the same till your sure she's fine. Keeping her separate might actually be a good thing as you'd know that your Roo's can't get to her.

 

You should plan on isolating your hen for about 3 weeks, if you want to be sure your own rooster is not the father of the chicks.

I agree with the other posters' concerns about diseases, but I also think that just having the birds together for a few minutes to mate would be less likely to spread diseases than introducing one bird into the other flock long-term. (Maybe have the mating happen outside of the usual chicken quarters, and pick up/throw away any droppings from the bird that is visiting, to further reduce the risk.)

You didn't ask, but regarding how often the hen needs to mate in order to keep producing fertile eggs: articles on artificial insemination recommend once or twice a week, so I'm guessing natural mating once or twice a week would probably also work.

Of course, artificial insemination could be an option to reduce diseases, but it sounds a lot more bothersome than just putting the birds together and letting them take care of the details!