FREQUENTLY ANSWERED QUESTIONS

EGGS

  1. Do scrambled eggs have birds inside them?
  2. How can you tell if an egg is fertilized or not?
  3. Are unfertilized eggs considered dead or alive?
  4. Can you see the 'sperm' or 'sperm sack' in a fertilized chicken egg?
  5. Is it safe to eat fertilized eggs?
  6. Is there a type of egg that does not have any yolk and only albumen?

EGG PRODUCTION

  1. How many eggs can a hen lay each day?
  2. Why have my hens stopped laying eggs?
  3. How can you tell if a hen is pregnant?
  4. Can hens lay eggs without roosters around?
  5. How can I tell which hens are laying and which are not?
  6. How many years can hens continue to lay eggs?
  7. Why do hens eat eggs and how can I stop them from doing so?

EMBRYOLOGY AND INCUBATION

  1. Can roosters be infertile?
  2. How can you make a hen go broody?
  3. How long after a hen lays her egg does it take the rooster to fertilize them?
  4. Does the temperature in the incubator determine the sex of a chicken?
  5. Can you incubate fertile eggs with a heat lamp?

Q. Do scrambled eggs have birds inside them?

A. Eggs purchased at the store are typically from commercial flocks in which there are many hens but no roosters so the eggs are never fertilized. If an egg is not fertile (i.e., infertile) there is no possibility of a chicken inside.

Q. How can I tell if an egg is fertilized or not?

A. It is not possible to tell whether or not an egg is fertilized without breaking it open. Once broken open the fertile egg has a small white dot on the yolk (which is the genetic material from the hen). If the egg is fertilized this dot looks more like a miniature donut. Some embryo development begins during the 24-28 hours it takes the hen to assemble all the parts of the egg. The clear area in the spot is the very tiny chick embryo. It is so small you need a microscope to see the embryo.

Fertile vs Infertile eggs

Q. Are unfertilized eggs considered dead or alive?

A. It depends on your definition of 'alive' - There is no specific definition of what is alive other than the fact that it is the opposite of dead. Life and death are terms used with organisms such as animals and plants. Since an infertile egg contains only the genetic material from the mother and does not have the potential to become a chick, it is not really an organism and thus would not be considered alive.

Q. Can you see the 'sperm' or 'sperm sack' in a fertilized chicken egg?

A. There are no sperm sacks in an egg. If an egg is fertilized a single sperm will have merged with the female genetic material to start the embryo. The chalazae are made up of egg white (albumen) that is tightly twisted and functions to position the yolk in the middle of the egg. If the yolk was not positioned in the center it could become adhered to the side of the shell and if an embryo is present it could become malformed or die.

Labeled parts of an egg

Sperm sacks, or storage areas, are located inside the oviduct of the hen - in the infundibulum and at the junction of the shell gland/uterus and vagina. It is these sperm sacks that allow female birds to continue to produce fertilized eggs for several days after a single mating. For more information on the reproduction system of female birds refer to the factsheet Chicken anatomy and physiology: Female reproductive system.

Q. Is it safe to eat fertilized eggs?

A. You can definitely eat fertile eggs. Fertile and infertile eggs look very similar and you won't be able to tell the difference without looking closely at them. They also taste the same and contain the same nutrients.

There are some people who will pay a premium price to get fertile eggs for consumption. On the other hand, there are others who will absolutely not eat them since it 'grosses them out.'. It is a personal preference. If you feel that life begins at conception for all animals, then in theory you are eating potential baby chickens when you eat a fertilized egg, but if the egg is not incubated the embryo will never develop into a chicken.

All eggs in the typical grocery store should be infertile unless otherwise indicated.

Q. Is there a type of egg that does not have any yolk and only albumen?

Labeled reproductive systemA. It is not typical to have an egg without a yolk but it can happen. Sometimes a little piece of the oviduct wall is sloughed off and stimulates egg formation as it passes down the oviduct so the hen adds albumen, shell membranes and a shell and the 'egg' is laid without a yolk. Since the female genetic material is on the surface of the yolk, and the yolk provides the nutrients for the developing embryo, a chicken that always lay eggs without a yolk would not be able to reproduce.

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EGG PRODUCTION

Q. How many eggs can a hen lay each day?

A. Because it takes 24-26 hours for a hen to construct an egg (adding the albumen, shell membranes and shell) and since chickens have only a single ovary and oviduct, hens are only able to lay an egg a day at the most. If you don't collect the eggs at the same time each day you might encounter a situation where one day you collected no eggs and the next two, but the eggs were laid on different days - just one right after an early previous collection and/or right before a late collection.

For more information on the reproduction system of female birds refer to the factsheet Chicken anatomy and physiology: Female reproductive system.

Q. Why have my hens stopped laying eggs?

A. Several factors could be involved - anything from genetics, management, health, to nutrition. Refer to the factsheet Why have my hens stopped laying eggs? for some suggestions.

Q. How can you tell if a hen is pregnant?

A. Chickens, and birds in general, do not get pregnant like mammals do (including humans). Their reproductive strategy involves laying eggs containing all the nutrients the developing embryo needs to hatch. Conversely, mammals become pregnant and carry their offspring within the womb receiving their required nutrients on an ongoing basis until they are born.

If a mature rooster is placed into a flock of hens, fertile eggs may be produced by the second day after introducing the rooster This is because an egg that is already 'in construction' in the female tract can't be fertilized (fertilization begins before the egg white is added). If the flock has many hens and only one rooster, it may require several days before mating of all hens takes place. It is typically advisable to have one rooster for every 6-8 females (depending on the breed of the chickens) and allow at least 4-7 days before expecting a high level of fertility in the eggs produced.

Female birds contain sperm sacks in their reproductive tracts which can hold sperm received during mating and release them slowly over time. As a result, a hen can produce fertile eggs for several days after a single successful mating. The sperm storage areas are not particular about where the sperm came from so if you have many roosters in a flock it will be hard to know which is the 'father' of any particular offspring.

For more information on the reproduction system of female birds refer to the factsheet Chicken anatomy and physiology: Female reproductive system.

Q. Can hens lay eggs if there is no rooster around?

A. Yes. In fact, the eggs you purchase in the grocery store come from hens kept without rooster their entire lives. The best analogy is a woman's monthly cycle - it happens each month whether she is sexually active or not. The same occurs with chickens, but on a more frequent basis than once a month.

Q. How can I tell which eggs are laying and which are not?

A. Depending on how long the hens have been laying, you can do a physical examination to see which of the hens are laying - but remember, they may all be laying, just not at a high enough rate to get 2-3 eggs/ day from your three hens. Refer to the factsheet Evaluating egg laying hens for suggestions on how to evaluate the level of egg production for individual hens.

Q. How many years can hens continue to lay eggs?

A. Hens are hatched with the total number of ova (the genetic material of the female found on the surface of the yolk) they will ever have, just as humans are. Males regularly produce new sperm, but the number gametes of the female are fixed at hatch.

Hens can lay for several years and the number of years will depend on the management and nutrition of the hens over those years. Breed also is a factor. The higher the rate of production in the first year or two, the less years she is likely to lay eggs. Some hens in backyard flocks lay eggs for 3-5 years but there isn't any research that has been done into how long they can lay before they go start 'menopause'. The oldest living chicken (at least documented) was about 13-14 years - although she was a hen, she did notlay eggs. She was used in a magic show and gets routine 'physicals.'

The productive life of hens is shorter than their life span. This needs to be taken into consideration when chosing hens for a backyard flock. If they become pets you either have to continue to feed them after they finish laying or find an 'end of life' option.

Q. Why do hens eat eggs and how can I stop them from doing so?

A. Egg eating can be a problem in some flocks. It is sometimes started because of a nutrient deficiency but it can also start for no apparent reason.

For some chickens it becomes a habit. Chickens are attracted to shiny objects and if an egg gets broken they will start pecking at it and eventually eat it. Once some hens get a taste of eggs they start breaking eggs to eat them. It can be a hard habit to break.

Make sure the hens are receiving a balanced diet and collect the eggs more frequently. Some people have had success with putting fake eggs (such as golf balls) in the nests to discourage egg eating, but it doesn't always work.

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EMBRYOLOGY AND INCUBATION

Q. Can roosters be infertile?

A. Hatching egg fertility (the number of fertile eggs produced by a flock) is affected by a number of factors - some affect female fertility and others affect male fertility. You can actually 'milk' a rooster to collect semen and examine it under a microscope to see if it contains active sperm.

Other factors include the type of lighting program and the ratio of males to females. Roosters, as with hens, are long day breeders in that they breed when days are long (more than 12 hours). The optimum ratio of male to females depends are the breed but are typically 1 rooster for every 6-8 females. If there are too many roosters they fight rather than breed the hens.

Q. How can you make a hen go broody?

A. Broodiness is a natural tendency for a hen to sit on her eggs to hatch chicks. Most hens eventually go broody, some breeds more often than others. For example, cochin and silkie chickens are considered champions at going broody while broodiness is rare in leghorns.

Broodiness is hormonally controlled so there really isn't much to do to induce it naturally. The stimulus for broodiness is often a nest full of eggs. However some hens will go broody without this stimulus. To reduce the incidence of broodiness in an egg laying flock, collect eggs daily from nests and hiding places. If a hen shows a desire to stay on a nest for extended periods, don't allow her access to the nest for several days. After a period of time, the broody behavior will cease and she will return to egg production.

Q. How long after a hen lays her egg does it take the rooster to fertilize them?

A. Chickens and other birds use internal fertilization. That is, the hen and rooster mate, and then the hen produces eggs. Once an egg has been laid, it can not be fertilized. It either already contains an embryo or it doesn't. Hens will lay eggs whether they are mated with a rooster or not. For more information see the factsheet on the anatomy and physiology of reproductive system of the female chicken.

Q. Does the temperature in the incubator determine the sex of a chicken?

A. The effect of temperature on the sex of the offspring is related to reptile eggs (such as alligators) and not for birds.

The sex of a bird is determined genetically and is set before the egg is even laid. Unlike mammals, however, it is the female bird that determines the sex of the offspring and not the male. In mammals the male is heterozygous (XY) and the female homozygous (XX) so that the male is the only parent with the Y gene which will result in a male offspring. In birds the female is heterozygous (ZW) and the male is homozygous (ZZ) so that the female determines the sex of the offspring.

While the sex of the chick is determined before the egg is laid, research has shown that male and female embryos may differ in their sensitivity to suboptimal conditions during embryo development. As a result, the ratio of males and females that actually hatch can vary depending on incubation conditions. This is because the ratio of males and females that do not hatch is affected not because the sex of the embryos was changed by the temperature (as happens with some reptiles).

Q. Can you incubate fertile eggs with a heat lamp?

A. While there is always the possibility, it is very unlikely that an egg heated by a heat lamp or regular light incandescent bulb will hatch. Eggs should be incubated at the correct temperature and humidity to get healthy chicks. It is very hard to regulate temperatures under lamps. If the temperature gets too hot or too cold the embryo will die or become deformed.

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