Why do chickens sometimes have double yellow eggs and soft-shelled eggs?

Sometimes, in a basket of eggs bought from the market, there is occasionally a big egg with almost two heads. When the eggshell cracks, there are two yolks in the egg, which are called double yellow eggs. It's strange, why can two egg yolks be wrapped in one eggshell? This starts with how hens lay eggs. The outer layer of an egg is an eggshell, which contains yolk and protein. Kill the hen and open its abdominal cavity. You can see that the yolk is like a bunch of grapes, round and rolling around, large and small. This is the chicken's egg. Mature eggs are sent to fallopian tubes, which secrete protein and eggshells, wrap the yolk and give birth to eggs. Sometimes, the hen's ovary function is too active, and two mature eggs enter the fallopian tube at the same time, and the fallopian tube can't be wrapped with protein one by one, so they are wrapped together in an eggshell, so double yellow eggs are produced. It is an abnormal physiological phenomenon for hens to lay double yellow eggs. Double yellow eggs don't hatch chickens. Sometimes, when protein secreted by fallopian tubes meets parasites or blood clots that fall into fallopian tubes, they will treat these things as egg yolks and wrap them into an egg layer by layer, resulting in a yellow-free egg. The main component of eggshell is calcium carbonate. So if the hen's food is short of calcium, the eggshell will be short of raw materials, so we should make the eggshell thin, even accounting for about 10% of the egg. One or two eggs and eggshells weigh one yuan, indicating that hens need a lot of calcium during the laying process. When raising chickens, we should not only prepare enough feed for hens, but also supplement minerals, such as limestone powder, shell powder and bone powder with more calcium. It is beneficial for hens to absorb calcium, so they will not lay soft-shelled eggs.