My understanding of this is a little different than what most in the thread are describing... There's several articles referencing the same study as this one:
https://www.google.com/amp/s/www.in...n-change-the-sex-of-chickens-1238516.html?amp
I can't find the study itself to see what the methodology is, but it seems like the uses would be pretty niche, and perhaps not cost-effective.
As I read it, its not refrigeration before incubation, but cooler temperatures(article says 'a few degrees') early in incubation that has the effect, probably very early.
And the effect isn't that it kills more male embryos(tho it certainly would lower hatch rates significantly). The effect is that a small number of genetically male embryos develop into hens. This is something that can even happen in humans, so it seems plausible enough.
So the way to test it would be to set your eggs staggered, maybe a day apart for 3-4 days. 24 hr after your last set, drop the incubator temperature. It says 'a few degrees' and probably means C, so let's drop it to 94° for three days. Accept significant hatch losses.
If any eggs hatch, gene test the hens.
If anyone's able to find the exact study and methodology, of course just copy that. But that's roughly what you'd have to do. There are several problems:
1. You'd almost certainly lose far more potential hens to hatch rate than you'd gain this way.
2. Expensive testing to see if you're successful, of keeping all hens for long enough to hatch enough eggs from them specifically to see if any were laying only roosters.
3. Even if successful, you'd still get roosters.
4. Most of us probably don't have the hatching capacity to reliably produce hens like this. What if it only happens 10% or the time, with a 50% reduced hatch rate? The ratios could be much worse, even.
5. Any hens produced like this would only have male offspring, unless you chilled them too haha.
I'd really like to see the original study, but I don't have the academic access to seriously hunt it down. Any one out there that does?
If this is what's been debunked, I'd be interested in seeing that debunking, I didn't find anything about that either.