For egg farmers, the most important thing after making sure their hens are healthy, is making sure that they are producing Grade A eggs. The biggest factor in this is egg shell quality.
Eggs are graded based on size, shell quality, and yolk quality. When an egg goes to a grading station they are washed, candled (see what this is here: Why ‘Candle’ An Egg?), and then sorted by size to be put into cartons. It is during candling when egg shell quality is assessed and when cracks would be found and removed. There are many factors (besides just a clumsy farmer) that can contribute to a cracked egg.
As a hen ages, the quality of the egg shells that she lays will eventually decline, causing more cracks to occur as the shells are more fragile. Creating an egg takes a quite a bit of calcium and so we increase the amount of calcium in the diet as the hens get older since she is not able to use the calcium as efficiently as when she was younger. Usually at around about 60 or 65 weeks old, we increase the level to the maximum level that it will remain at for the rest of the time we have them. The calcium in the diet it mostly oyster shell.
Another factor that can lead to cracks is equipment malfunctions. To get an egg from the hen to the carton is a process that involves transporting the eggs quite a distance. To see how it happens on my farm check out this video: Getting Eggs to Your Table. If one little thing is off, it can mean the eggs are transported rougher than normal or allow an egg to hit an edge faster than it should and it can cause a crack. So as farmers, we are regularly maintaining and upgrading our equipment to ensure safe and happy hens and a good quality product.
Of course the biggest factor of cracks is the most important – breaking them into a pan to eat! So next time you crack open an egg, you can be sure you know how the farmer ensured it was Grade A.