There may come a time when you need to seriously investigate whether or not your rooster is doing his job. If you are interested in hatching chicks, it is important to know that the eggs on which your hens are sitting have been properly fertilized. There is not much worse than a hen spending 21 days trying to hatch eggs that were not viable. That amounts to three plus weeks a broody hen has wasted sitting on the nest in addition to the time it will take to get her back to laying again when in her mind she was supposed to have chicks to mother.
Roosters could be falling behind on their job duties for many reasons. It could be something as simple as that he did not mate with each hen in turn so that all of them laid fertilized eggs, such as in the case of a large number of hens being present. Or perhaps your rooster is growing older and becoming infertile himself. He may be making a valiant effort at egg fertilization, but time and age could be slowing down his progress. If your rooster is ready for retirement as a breeder, the sooner you know, the better, and the less egg waste you will have on your hands.
One way to tell if eggs are fertilized or not is by candling them. This method has been used for many years by farmers and lights made specifically for this purpose are sold in many livestock and feed supply stores. It is done by holding eggs up to a light source in order to locate the embryo. In some cases, eggs may appear opaque, which is another sign of fertilization. If you candle eggs over a several day period, in a fertilized egg you will see the air sack diminish in size and notice the growth of the embryo. Eggs that are not fertilized will have a yolk that seemingly floats freely and is consistent in color.
If you want to know if eggs are fertilized more out of curiosity than because you are truly trying to hatch chicks, you can check whether your eggs are fertilized are not by cracking them open. When cracking an egg, be careful not to bust the yolk as this will distort it and make it harder, if not impossible, to locate the telltale spot that makes fertilization known. With your intact egg yolk resting in a bowl or pan where you can see it clearly, look for a white spot. If it presents as a solid white dot, the egg is not fertilized. This is known as a blastodisc. If what you see is instead more of a bullseye, the egg has been fertilized and what you are seeing now is known as a blastoderm. A blastoderm is a blastodisc that has been fertilized by sperm.
It only takes about two days after a mating for the creation of fertilized eggs. Once fertilization takes place, a hen can go on to lay fertilized eggs for up to about three weeks after the initial mating occurred. If you wish to breed a specific hen and rooster combination, your hen will thus need to go three weeks without exposure to any other roosters to ensure she will produce eggs fertilized by the desired rooster. While differentiating between eggs that are fertilized and those that are not can be tough, it is an important skill to develop if you intend to hatch eggs at some point. Arm yourself with a proper light and some eye glasses if necessary before getting started. Also be sure to look at as much reference material as you can beforehand in order to be able to tell with confidence which eggs have been fertilized and which have not. This will aid you in having not only less egg waste but also happy mother hens with chicks that will in time go on to lay their own eggs for you as their mothers did.