| Double-yolk eggs are usually laid by young pullets that have just begun laying. From what we've seen around our farm, they're more common in larger breeds of hens like Columbia Rocks, Rhode Island Reds, and Barred Rocks. They are also mainly from chickens that are well-grown and in good condition. We don't keep hens anymore, but do get eggs from either a friend's farm, or from the store. The free range hens at our friend's farm occasionally have double yolks. The store-bought eggs that we get -- I don't eat eggs, but Mr. Croc always buys extra-large eggs from a particular farm that keeps free-range, grain-fed (no animal protein) hens, and they usually have about 4 to 6 double-yolks per dozen, which seems high, but then, these eggs would be from the above described hens that are just beginning to lay eggs. If you're buying mainly medium or large eggs, you will probably only rarely see a double-yolk egg. Likewise, I think that most battery hen operations have their hens on such a controlled ration that there's probably little chance that they would lay double-yolk eggs. As for whether double-yolk eggs would produce 2 chicks, I've never heard of that and imagine that it's not possible. I used to keep quite a lot of hens at one time, and I used to collect and incubate eggs. I've never seen that happen, but it might be the reason that some of the eggs wouldn't develop and had to be discarded when I candled them part way through incubation. |
