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It’s a reasonable question but really hard to answer. It depends a whole lot on your set-up and goals.
Some people say they have lower fertility in the winter and others say it’s not a problem. I suspect there are some differences other than just the weather involved. I have a bunch in the incubator right now. I candled and have pretty good fertility, about the same as in warmer months.
If you incubate in the house, the outside weather really doesn’t affect that. If you are subject to extended power outages, you might want to think about that.
Where do you plan to brood them? My brooder is in the coop. I just keep one area warm and let the rest cool off as it will. Sometimes the rest of the incubator gets pretty cool. When a broody raises chicks, she does not heat the entire world. She provides a warm place for the chicks to go to when they need to warm up. I work off the same concept. It works for me. I have no idea what your facilities are like or how you plan to manage them.
By raising mine in the coop and letting them get acclimated to cooler temperatures, I can take the heat away earlier than someone that keeps them in warm conditions. To me, there is not a magic age that they can go outside. It depends on your weather, the conditions they are going into, and how well they are acclimated to those conditions. I’ll give a couple of examples.
Last summer when we were having a triple-digit heat wave, I took the daytime heat off chicks in my brooder at 2 days. The overnight heat stopped at 5 days. Days, not weeks. They were telling me by their actions they did not need the added heat.
Last fall I kept heat on the chicks in the brooder for 5 weeks. That was just in one end. The rest of the brooder cooled off quite a bit. Overnight lows were in the mid 40’s Fahrenheit. They spent a lot of time in the cooler parts of that brooder. When they were 5 weeks old I moved them to my unheated grow-put coop. Both brooder and grow-out coop have good draft protection and good ventilation. There were about 20 of them so they could help keep each other warm if they needed to. When they were 5-1/2 weeks old, the overnight temperature dropped to the mid 20’s Fahrenheit. They were fine but if they had not been in that brooder where they could get acclimated, I’m not sure how well they would have done.
Those are examples of why I don’t think there is one magic age that suits everybody.
Something else to consider. What are your goals for these chicks? The earlier in the year you hatch them, the earlier they will start to lay or will be ready to eat. The later you hatch them the better your outside temperatures will be. If you wait until really late to hatch them, they may not start to lay until next spring. If they start to lay this fall, there is a reasonable chance (A chance. I don’t give guarantees) they will skip the molt and lay straight through until next fall.
I don’t think there is a perfect time for everyone in your climate. There are a few trade-offs and some things you will have to deal with whatever you choose. Good luck whatever that choice is and once again
