Thanks, I am a Zoologist and work as a Biology teacher in high school.
In my opinion it is the fertility of your breeding stock. Do you give the some vitamins boost,( at least once a weeki) especially at winter? I give my chicken once a week soluble vitamins in their FEED!, l ferment 50% of their feed, they gey every day shredded vegetables especially carrots and green and do on.
I have done that on.... rhinos! Enter to my BYC interview if you want to know more!
I feed a game bird breeder feed this time of year. it has a few more vitamins and minerals than the chicken layer feed does.
The breeding stock does not get table scrapes. Greens are hard to get this time of year. As is sunlight. I have had them on artificial light since the end of November. The roosters fertility is what I think it is. I also think many eggs freeze and kill the embryo.
I have wondered if I could find a water soluble vitamin for them. The risk would be over doing it, or wasting it. My water freezes fairly quickly in the coops most days.
It is just not natural to hatch in the winter in Minnesota. I know in 3 months my hatch rate will soar to 90% plus. but it is depressing this time of the year.
Thanks!