The 25 hour thing for an egg to go through the hen’s internal egg making factory is an average. Some take longer, some go faster. The other part of it is that there are different triggers for a hen to release an egg yolk to start that internal journey in becoming an egg. One of the normal triggers for most hen sis when one egg is laid the next starts that journey. But different triggers affect different hens differently. Another trigger that is fairly strong is daylight.
I once had a green egg layer that laid her egg before 9:00 am every day for a week or more at a time and then skipped a day. Her cycle was certainly not 25 hours.
They may have counted the eggs but did they mention the quality of the eggs? Occasionally some hens might mess up and release two yolks in the same day. If the yolks are released at the same time the hen may lay a double yolked egg. If the release times are separated a bit, then the hen can lay two eggs in the same day. A potential problem with this is that a hen often makes just enough of some types of egg material in a day to make one egg, not two. It’s fairly normal for the second egg to have either no shell or a very thin shell. Even when there is enough shell material, you can get defective eggs like the last two on this poster.
http://www.alltech.com/sites/default/files/alltech-egg-shell-quality-poster.pdf
Aldavis, each rooster is an individual. Some start out really fertile (actually most do) and remain fertile for different lengths of time. A lot of that has to do with their vitality. A younger rooster typically is more active than an older rooster. There is not a magic age when roosters all go from fertile to infertile. Health, nutrition, heredity, and even how much competition they have from other roosters have an effect. Some roosters, especially those one to two, often three years old have no problems keeping 25 or 30 hens fertile, some, especially older ones, may have problems keeping five hens fertile.
My suggestion is to monitor the fertility of your eggs and add a new one when fertility starts to drop. That’s basically what hatcheries do. They find that by adding a younger rooster to the flock they can often stimulate older roosters to become more active.
How many hens do you need for five dozen eggs a week? That’s really hard to answer accurately. Different hens lay a different number of eggs per week. Some may only lay an egg every other day if that. Most production breeds will lay an egg a day for anywhere from 4 to maybe 9 days in a row, then skip a day, then they will go through that cycle again. So it can vary a lot by the individual hen.
A laying flock follows a fairly regular production curve if you have enough hens for averages to mean anything. Normally they start out slow but quickly ramp up to maximum production. Then, over time, production slowly decreases. After maybe a year to 14 months of production their lay rate drops to maybe 60%. This is for commercial flocks composed of egg laying hybrids. 60% is normally when profitability drops to where the flock owner has to decide to either let them molt so they can recharge their system or replace them with a younger flock. Normally after their first adult molt they come back laying great and the eggs are bigger. Then they go through that production curve again. But after their second adult molt their production drops maybe 15% to 20%. They are normally replaced when it’s time for their second adult molt.
All this is for commercial hybrids. You probably don’t have those so your numbers will probably be different, but they will follow a similar pattern. They also manage the lights to maintain production. A lot of us don’t do that so our hens typically stop laying and molt in the fall, then come back laying great after the molt is over, though some wait for the longer days of spring to start.
It’s not as set answer, it will vary depending on how productive your hens are and what art of that production curve they are in. It’s going to change throughout the laying cycle.
