I know this is long, my posts often are. I’ll put the summary up front. They do not need a specific length of daylight to lay. Although the days getting longer and shorter have a big influence, especially on mature hens, I’d expect most of your RSL pullets to start laying fairly soon whether you add extra light or not, but adding extra light can go a long way toward getting them started. As long as you allow them to molt every 12 to 18 months, adding supplemental light does not harm them.
Now I’ll justify my summary. And don’t worry about that months/weeks thing. I’ve done much worse.
Here’s the response I got when I questioned a poultry reproductive specialist about a hen running out of ova that develop into eggs.
Yes, a young Pullet chick hatches with a determinant number of follicles on her left ovary that are possible to be developed to become one of the yolk or ova in an egg. Only the left ovary develops in most avian species so anything on the right ovary never develops and is of no use. So can a hen theoretically 'run out of' potential follicles? Yes she can and this does occur on occasion. It happens often in parrots that may live 70, 80 or even up to 100 years of age. These hens that run out of follicles are referred to as 'slick hens' as the ovaries are often checked by veterinarians and confirmed that they are indeed 'slick' hens with 'slick ovaries' that have no more follicles to develop.
So does this happen often in chickens? Not really that often because most of our domestic chickens do not live long enough to run out of follicles, they 'run out of gas' in other ways much sooner. This could be some other disease or infection or condition related to extended periods of laying that might either cause death or an inability to produce and develop proper shells on an egg.
So in short, yes it's possible but unlikely for a chicken to become 'slick' and run out of follicles.
Keith Bramwell
Dept of Poultry Science
University of Arkansas
That’s a good article that Aart linked to. I’ll make a couple of comments on it.
First, Dr. Petrik puts a requirement on what he says. The hens have to molt every 12 to 18 months. If they are not allowed to molt that changes what he said.
He mentioned that to keep your hens laying you need to keep their day longer than 13 to 14 hours but that they will stay in production in less light than that if they are not exposed to the longer days of their summer, wherever he and the author of that article are located. It’s not the length of day that is so important, it’s whether the days are getting longer or shorter or technically whether the nights are getting longer or shorter. It’s the dark period getting longer that triggers the molt and they stop laying.
Qstarbird, in Ohio your longest day is going to be somewhere around 15 hours, your shortest maybe 9 to 9-1/2 hours. There is a forum member in Pennsylvania, which has about the same day length as you, that provides 14 hours of light and her hens still normally molt. That one hour loss of light is normally enough to trigger a molt for her in her older hens.
The main point of all this is that if you provide extra light then it is important when you start and stop it. If you stop it before the natural length of day matches the amount of light they are seeing, you can trigger a molt, even in the middle of spring when they should be laying like gangbusters.
As Aart said, pullets in their first year often lay throughout their first winter without extra light. Most of mine normally do but they always molt in their second fall/winter. I do not provide supplemental light and my shortest day is 9 hours 40 minutes.
When will yours start to lay? I don’t know. I’ve had plenty of pullets start this time of year with the days still getting shorter. A couple of times I’ve had pullets start to lay in early December, the shortest days of the year. Obviously those didn’t need 14 or 15 hours of light a day to lay eggs. I’ve had hatch mates of those wait until the days are getting longer in the spring to start. It does vary by individual. With RSL’s yours should tend to start when they are mature enough regardless of length of day but these things don’t come with guarantees.
One strategy you might want to employ is to pick a day and start extending the length of day gradually to start them laying. As Dr Petrik said they might need several weeks to make the changes internally to prepare to lay, but if they are getting ready this can kick start them pretty quickly. Remember to maintain that day length until the natural day length is the same. It will require regular adjustment. Many people don’t do that and still don’t trigger a molt when they stop the extra light, but sometimes it does.