How to Tell a Fertile vs INfertile Egg (Pictures)

Thought you'd like to see this since so many have asked how to tell if their eggs are fertilized. The first picture is an INfertile egg. The next two are fertile eggs at slightly different stages, but both freshly laid. Usually, you look for the bullseye/donut appearance, but there are different stages of development of even freshly laid eggs and the two last pictures demonstrate that. This is caused by cells in the center of the blastoderm dying off and leaving a cleared out area, making that bullseye appearance.






From this web page:  http://www.hatcheryoffice.com/embryology/determfert.htm

No, the first one is NOT fertile. See the difference?

No, the embryo isn't dying. The cells are sloughing off and making an area thinner so it appears to have a bullseye. I didn't mean the embryo was dying, just certain cells. The last picture is further development from the middle picture. Here is the scientific explanation:

a Stage VII blastoderm is 2-3 cell layers thick at the periphery of the blastoderm and 5-6 cell layers thick in the center of the blastoderm (Figure. 1). If this developmental stage is viewed with the naked eye the blastoderm is a round uniform shape but is a solid white color with no donut shape. When examining a fresh egg, the white embryonic mass of cells may look similar to Figure 2. As development proceeds, cells from the center area of the blastoderm start to die off due to a pre-determined genetic program that tells the cells to die (apoptosis). These dying cells fall into the subblastodermic cavity (Figure 3). The death of the cells progresses producing a transparent thinned-out area in the center of the blastoderm. This thinned area is only one cell layer thick, while at the periphery of the blastoderm the cell mass is still three to five cells thick (Figure 4). This cell shedding produces a Stage X of development and is the most common stage of development in a freshly laid chicken egg. At Stage X, light passes through the thinned one cell layer thick area of the blastoderm, but is reflected off the 2-3 cell layer thick area at the periphery; this effect produces the donut appearance of the blastoderm (Figure 5). The center or transparent region is called the area pellucida and the peripheral area that forms the donut shape is called the area opaca. It is only the cells of the area pellucida that will eventually form the cells of the embryo.

I was actually glad to find the first fertile egg pic without a clear bullseye because I just had an egg that didn't seem INfertile, but also didn't quite look fertile, as I was used to seeing a fertile egg. I just wasn't quite sure, but I had a feeling. That particular picture confirmed that the egg in question was probably fertile, to my delight.