When you crack open the egg, if it's fertile, you'll notice a small white spot on the top of the yolk about 4mm in width. This is called the germinal disc. This is what tells you if the egg has been fertilised. This disc is formed with a single cell from the female and a single sperm from the male.
Each egg has a tiny white spot in the yolk. This white spot is called the germinal spot. In eggs that are not fertilized, the germinal spot is a small collection of the hen's egg cells. However, if the egg is fertilized by the rooster, the germinal spot will be bigger and appear as a circle with a white outline.
How long does a rooster need to be with a hen for fertilisation to happen? It can range from a once off meeting to around 3-7 days on average.
A hen does not know if her eggs are fertilised or not. In fact (much like a human) a rooster can be infertile, so a hen's eggs might not be fertilised even if she is in a flock with a rooster. Many modern breeds and commercial hybrid hens will do nothing with their eggs other than lay them and walk away.
Non-Fertile egg, Notice the Germinal spot just above center on the Yolk. It appears as solid white spot. Fertile Egg. Notice the germinal spot looks larger and like a circle in this fertile egg.
The oldest and easiest way to tell if an egg is fertilized is called candling the egg. It is literally holding the egg up to a lit candle {not to warm it, but in order to see inside of the egg}. You can also use a very bright small flashlight. If the egg appears opaque, it is probably a fertilized egg.
This is all fine and dandy if your chicken does have eggs to hatch, but sometimes, a chicken will sit on unfertilized eggs or even imaginary eggs. Hens raised without roosters can't lay fertile eggs, but they can still go broody and attempt to sit on a clutch of eggs.
Now you know, fertilized eggs are completely safe to eat—unless you've neglected to care for them or wash the eggs…or you've let your broody hen have her eggs for longer than normal. You can safely eat your fertilized eggs without any worries. It's truly no different than an unfertilized egg.
Generally speaking, a hen who has mated will be fertile between 7 and 10 days after. It takes that long for the sperm to reach the oviduct where eggs are made.
During mating, the rooster stands on the hen's back, holding her neck feathers with his beak and steadying himself with his feet. This activity is known as treading. Eventually, the rooster may come to have a favorite hen or two in the flock. Those hens may end up with bald patches on their backs.
A rooster may mate from 10 to 30 or more times per day, depending on the availability of hens and competition from other roosters. However, the number of sperm per ejaculate is seldom less than 100 million which is the minimum required to maintain high fertility.
A rooster in his prime can 'cover' 1-16 hens. As he ages, he can successfully cover fewer hens, at age 3 years he is considered 'beyond prime'. A rooster's job is to ensure the success of his kind so mating with the hens looms large in his mind for many of his waking hours.
According to Michigan State University Extension, egg color is determined by the genetics of the hens. The breed of the hen will indicate what color eggs she will produce. For example, Leghorn chickens lay white eggs while Orpington's lay brown eggs and Ameraucana produce blue eggs.
MYTH: Fertilized eggs taste different from infertile eggs. FACT: There is absolutely no flavor difference between fertilized and unfertilized eggs. MYTH: A blood spot inside the egg means the egg is fertilized.
Chances are you've never eaten a fertilized egg, because nearly all eggs sold commercially are produced by hens that have not mated, says Lauren Cobey, media representative for the American Egg Board. The difference between fertilized and unfertilized eggs comes down to whether a rooster has been involved or not.
The average duration of fertility is about 10 days.
When you crack open the egg, if it's fertile, you'll notice a small white spot on the top of the yolk about 4mm in width. This is called the germinal disc. This is what tells you if the egg has been fertilised.
A general rule, unwashed eggs will last around two weeks unrefrigerated and about three months or more in your refrigerator. If you're experiencing an egg boom, it's smart to refrigerate any unwashed fresh eggs you aren't planning to eat immediately. This will help them last longer.
Cleaning and Storing Eggs
Otherwise, the eggs can be stored on the counter for up to a month or stored in the refrigerator; it's personal preference. I think the eggs taste better within two weeks, but they're fine to eat within a month of laying. If the eggs have a little manure on them, remove.
Find out by candling
If the egg is fertile, then you should see a dark spot around the middle of the egg, with some spider-like veins beginning to form around it. If its not, you should just be able to see the shape of the yellow yolk inside the egg, without any signs of an embryo or veins.
Happier Hens
The hens experience a state of order and liberty that they didn't have before. Without a rooster, the most aggressive and dominant hen would usually take over and be a bully. With a rooster, everyone, even the weaker members of the flock, can rest easy.
Correct ratio of hens to roosters:
A good ratio is 10 hens for every 1 rooster. Roosters are very protective of “their” hens, and if there are too many roosters in your flock this can cause fighting over another rooster mounting a hen that is not “his” hen.