Is there a way to encourage double-yolk eggs? One of my hens gave me one recently and I was wondering what caused it and if it could be persuaded?
Double yolk laying hens can be selected for with selective breeding for larger egg size. Some breeds like delawares that lay large eggs tend to lay more double yolkers, with some strains such as the one from Sand Hill laying a significant number. The problem with double yolk laying hens is that fertility is reduced and you will only get an egg every other day as opposed to every day with single yolked eggs. Double yolkers can also eggbind your hens as they are sometimes too large to pass easily. Double yolk eggs can be incubated and hatched but they typically have a very low hatch rate as there is not that much room for two chicks to develop. You can think of the hens reproductive tract as an assembly line with various steps; first the yolk and the white are made and then just before laying they are enveloped in a shell. If something goes wrong and things get jumbled up, the internal parts of the egg go through the line a little too fast and get enveloped in the same shell. Typically a yolk is made every 25 hours or so, but sometimes two are made in the same day and get wrapped up in a single shell instead of two.
I get a double yolk egg 2 out of 3 days a week. No quite every day. Sometimes they are not much bigger than a normal egg.
