I don’t know about chickens, but we breed snakes and have had two snakes emerge from the same egg. They are much smaller than their other brood mates and don’t always make it, but it happens. This is just my swag, but snakes generally have more wiggle room in their eggs than chickens, so I would bet that chicken egg twins wouldn’t both survive too often. I bet the doubles most often end up “duds”, but again, I am just guessing.
I had a double chick egg when we did our embryology unit in 5th grade. My teacher wanted to throw out my egg and give me another, but I begged and pleaded and he let me observe it. They both got big enough to fill the shell, then one died, and I guess the other caught an infection or necrosis or something and it died also. The teacher wouldn’t let me open the shell to do a necropsy. :mad:
Why do you breed snakes? Sounds interesting.
Some breeds lay more double eggs than what is the common factory breed. There was a smaller breed on some local farms that laid smaller tan eggs and had many double yolks. I’ve always wanted to see eggs from the breed that lays blue eggs. You did get to try many different eggs when every farm had a few chickens, and they liked to get a few odd birds for the novelty.
My husband was involved with it before I met him - before him, I didn’t realize that such things happened but there is actually a very big subculture of people who keep and breed reptiles as pets. Here in the Chicago area, there are reptile swap meets once a month. There are many different types of snake that people keep as pets and many different color variations within the types. The more rare and beautiful “morphs” can get really pricey (and therefore profitable to breed and sell).
The first question people who have never heard of the hobby always ask is, are any of them poisonous? No, it is illegal to keep venomous snakes as pets in nearly every state (Texas, Wisconsin, and Kentucky are the only ones who allow them, to my knowledge).
People keep corn snakes, king snakes, milk snakes, ball pythons, red tail boas, rosy boas, and sand boas to name a few. We are actually getting out of it, though - we don’t have the time to dedicate to it, and the market seems to be reaching something of a saturation point. www.kingsnake.com is a good place to go to see classifieds and forums dedicated to the reptile hobby.
I’m here! It took a couple of days, but finally my Chicken sense went off! Need to fine tune that thing.
Double Yolked Eggs
Like others have posted already, two yolks in one egg are more common for young hens whose reproductive systems are going like gangbusters, and older hens who have a genetic predisposition towards large eggs.
Hens ovulate about once a day in response to hormones, but the hormonal release is light controlled. Long daylight hours stimulate the hormone release from the brain, and the fluxuating levels cause ovulation similar to humans. Although chickens and most other birds only have one ovary, that ovary is covered with yolks that are waiting to be ovulated. It looks like a big cluster of yellow grapes. If a yolk is at the right stage of development when the right sequence of hormones hits, then the yolk is ovulated. The yolk then travels down the fallopian tube and uterus, where the egg white, membranes, and shell get added.
Young hens, like young women, have ovaries that are full to bursting with developing eggs. When the ovulation hormones hit, they often have two yolks (or eggs in humans) that are ready to go. Both eggs travel down the fallopian tubes and uterus together and end up stuffed into the same shell.
Older hens who have a genetic predisposition towards large eggs are a little slower reproductively. Older hens lay bigger eggs than young ones anyway because their bodies are more used to the process. However, it takes time to add all that egg white. Because the ovulation cycle is slightly more than 24 hours, and finishing an egg completely takes another 24-26 hours, there can be overlap, and the hen might ovulate again before the first egg is completely finished. When that happens, she might decide to deliver the first egg prematurely, and you get a floppy egg thing with a thin calcium outside, or she might stick both yolks in the same shell. It just depends on how close together things happened.
All commercially produced eggs are sorted using a machine. The hand technique hasn’t been used since my mother’s grandmother’s time. The eggs are collected and placed in a big flat, and then backlit. A person looks over them all over and touches any problem eggs with the point of a special wand. The wand is connected to a computer in the ceiling, which calculates the egg’s position in the flat based on the angle the operator moved the wand into when she touched the egg. The operator can also tell the computer exactly why the egg needs to be pulled. The eggs then move down the fancy conveyer belt which reconfigures to move the marked egg out of line and into the appropriate collection basket.
Generally, producers don’t like to put double yolked eggs in with other eggs because, as folks have pointed out, they don’t fit in the cartons and are prone to breaking. Since one broken egg means the other 11 don’t get bought, it’s worth pulling them out.
Double yolked eggs, and other strange but perfectly safe eggs like blood/meat spots and peewees, can usually be bought directly at the farm, if the farm has an on-site store. Most do.
Chicks started from a double yolk rarely make it to hatching stage. As you found out, there just isn’t enough space and air and nutrients in there for two. Also, the process of hatching is pretty coordinated and would be screwed up for two. I’m curious, how do you know one died before the other?
You’re thinking of Araucanas They tend to be more of a blue-green than robins’ egg blue. Still neat.
From candling the egg to see their hearts beat. One stopped, in my memory, about 3 or 4 days before the other. Of course, that’s a 23 year old memory of a 10 year old, so it could be exaggerated, but I do know there was *some *span of time with one beating heart and one not.
We each marked our egg with our initials and candled it each day to draw what we could see and write down our observations. It was a really cool teaching unit - I think the teacher got the incubator, eggs and several bright lights for candling all as a kit. Our district did it every year with the fifth grade class.
I have no idea what happened to the chicks that *did *hatch, come to think of it! :eek:
One week, both my neighbor and I ended up getting a double-yolk egg in our dozen from the supermarket.
I just had a double-yolker last night. Huge sucker, that egg was, too – a good 25% larger than the other eggs in the carton. It was delicious. 
Our eggs come from my wife’s parents though, who keep chickens for this purpose.