Do egg production farms swap out their hens every year? I have been told they sell them after they are a year old.
The commercial egg laying operations are a business. To stay in business they have to make a profit just like any other private business. They use hybrids special bred to be laying machines. The birds are relatively small in size so more of what they eat can go to making eggs instead of maintaining a larger body. That gives a good feed to egg conversion ratio. They lay relatively large eggs for their body size. The goal is Grade A Large.
They mainly control when the pullets and hens lay by manipulating lights. Diet and other things factor in but lighting is the big component. Once they start laying they lay really well for a long time. But eventually their bodies start to wear down. The number of eggs and the egg quality starts to suffer. The quality and number of eggs drop to a point it is no longer profitable to feed them so they are faced with a choice, either replace them or feed them through a molt so they can refresh their bodies. They use production records and have graphs and formulas to help them make that decision. After the molt the hens are back to laying a lot of good quality large eggs. Sometimes they decide to replace them after one laying cycle, sometimes they keep them through two laying cycles. Each laying cycle is somewhere around 13 months. I don't know if the ones you are looking at have been through one or two laying cycles.
After the first adult molt they come back laying really well, just like the first laying cycle. Plenty of eggs and probably a bit bigger. But every adult molt after that first one they reduce laying. A flock of 5,000 laying hens will typically average about 15% fewer eggs a week after the second adult molt. The reduction is enough to make it more profitable to replace them with pullets than feed them through another molt. Some hens will reduce more than 15%, some less, but the overall flock average is around 15%. These are the commercial laying hybrids. Our typical backyard breeds also go through a reduction after adult molts but I don't know if they stick with this 15% or not. Probably not.
What does a 15% reduction mean in eggs? If a hen were laying 7 eggs in an eight day period, a 15% reduction means she would only lay 6 eggs in an 8 day period. Not horrible for a backyard flock but enough to make them not profitable to the commercial guys, considering you have to feed them through a molt before they start laying again. But remember, this is flock average. You may get an individual that petty much shuts down or one that does not reduce at all. Three hens is not enough for averages to mean much.
These commercial hybrids are highly tuned egg laying machines. They are susceptible to medical problems related to egg laying. They are bred to have a really good feed to egg conversion ratio and their bodies are relatively small for the size egg they lay. Commercial operations feed them a layer ration that is about 16% protein. If they fed a higher percent protein feed the eggs would be even larger. That means they would be more susceptible to medical problems due to laying larger eggs.
I see on here all the time where someone gets these hens and is horrified by how they look. They are so small and the feathers look so rough. I have to feed them really well so they can recover. They are probably not doing those chickens any favors. They are bred to be pretty skinny. They are probably ready for a molt or already molting. When a hen loses a lot of feathers they look a lot smaller. I butcher a lot of chickens, it can be surprising how much that we see as body size is just feathers. If you are one that feels you have to feed a lot of protein I urge you to not get these. Feeding them really well can lead to prolapse, internal laying, or them becoming egg bound. These highly tuned egg laying machines are pretty much at that edge anyway. Feeding them really well can push them over that edge.
Before you get these find out what they a have been vaccinated for. Most vaccinations won't cause any problems but one that is sometimes given can make that bird a carrier for that disease and it can infect others. I can't remember which one it is, it has been years since I looked it up. All the other birds in that commercial flock will have the same vaccinations so they are protected but your current birds are not. Not all commercial laying flocks receive the same vaccinations so it's up to you to determine what these have received.
I have never personally gotten any of these hens. They just do not fit my goals. I knew a guy that regularly got 10 of them, fed them through a molt, and got really nice egg production the next year. Then he put those hens in the freezer and got 10 more.
