Diagnosing and troubleshooting incubation problems and hatch failures

Eggs failing to hatch can be a disappointing and sometimes costly experience and finding the cause of the problem can and will help prevent future losses. Failures to hatch can either be caused by a problem with the breeder flock, incorrect handling/storing of the eggs, or incorrect incubation techniques/incubator settings. In this article I will break down the causes of hatch failures, starting with...

The breeder flock

The breeding cockerel needs to be young, not immature, and in good health. In general males mature at the same rate as their female hatch mates of the same breed, so when the females from the hatch are old enough to start laying, the males should be able to fertilise their eggs. Very young males tend to have a lower sperm count, so check fertility before setting eggs. Avoid using really old males for breeding as their sperm can be abnormal, resulting in infertile eggs. Too many females, too few males and overcrowded conditions can also cause infertility. A good ratio to ensure fertility is no more than 10-12 females to 1 male.

The hens in the breeding flock need to be mature, in good health and laying even shaped, normal size eggs with strong shells. Pullet eggs (a young hen's first few eggs) can be incubated, but it is not recommended. Remember, small eggs = small chicks. Rather wait a week or two for the pullet to get her reproductive system in gear and all the funky "practice eggs" out of the way. Avoid using eggs from really old hens as these eggs show a higher incidence of infertility, early embryo mortality (0-4 days) and late hatches.

Healthy hatching eggs starts with healthy hens. Do not incubate eggs laid by sick hens. Sometimes the eggs themselves will show signs that something is amiss with the hens. Some signs are corrugated, fragile, or rough shells. More info on that can be found in this article. All hens, especially hens used for breeding, need to be fed well in order to lay well, so make sure the hens are fed a good quality layer ration. Inadequate nutrition in the hen's diet can result in inadequate nutrition in her eggs, resulting in embryo development problems, embryo mortality and sometimes handicapped chicks.

The hatching eggs

Malformed eggs are unsuitable for hatching and damaged eggs, unless they are very valuable, should rather be used in the kitchen or discarded. A small crack in the shell can be repaired with candle wax (preferable birthday cake candles, as these melt at a lower temperature), or nail polish. Abnormally large eggs should also be avoided. These often contain more than one yolk and though double yolk egg hatches are possible, very few are successful. Soiled, or dirty eggs carry the risk of contamination, spread germs in the incubator and may end up spoiling the eggs. Remember, bacteria thrive in a warm, humid environment! It's best not to wash the eggs selected for hatching as this will remove or damage the protective bloom covering the egg shell, which helps keep harmful bacteria out. Therefore it is better to select clean eggs for hatching.

**Make sure your hands are clean when handling eggs and that your incubator is cleaned throughly between hatches.

Hatching eggs should ideally be stored no longer than 10 days before setting. An epidemiological study of Dutch hatchery data (Yassin et al. 2008) showed that, on average, each extra day of storage before the seventh day reduced hatchability by 0.2%, rising to 0.5% after the seventh day. Old eggs can also cause a range of hatching problems (see below). If possible, store eggs in a cool room (60-65*F) and a humidity of 45% - 75% and set them within a week.

**Avoid using eggs laid during the withdrawal period (usually 2 weeks), after medicating, or deworming hens. Certain medicine's residue can interfere with embryo development, resulting in dead embryos, or malformed chicks.

*You can check for fertility in the eggs by cracking a few eggs on a plate and looking for the little "bullseye" on the yolk. Some wonderful pictures illustrating this can be found in this thread. If most or all the eggs tested are showing signs of being fertile, chances are that the rest of the eggs from that pen will have good fertility and can be incubated.

Causes of failure to hatch and embryo mortality

Day 1 - Eggs infertile

- Immature males, males with abnormal sperm, females with abnormal eggs (germinal disc). Most often seen with very young, or very old breeders.
- Too many, or too few females per male, resulting in infrequent mating.
- Extreme weather conditions.
- Disease in the flock.
- Overweight breeders, especially males.
- Nutritional deficiencies and/or incorrect feeding.
- Administration of certain drugs and/or use of pesticides/chemicals in or near the coop and run.
- Infestation of parasites, such as mites.

Day 2 - Egg fertile, no development

- Eggs stored too long prior to setting.
- Eggs stored under incorrect conditions, for example at too high/low temperature.
- Eggs damaged during handling, or transport.
- Incubation temperature too high.
- Very young, or very old breeders.
- Hereditary, inbreeding, chromosome abnormalities or parthenogenesis.
- Disease in the breeder flock.

Day 3 - Dead embryo

- Eggs stored too long, or under incorrect temperature.
- Too high, or too low temperature during incubation.
- Eggs damaged during transport.
- Disease in the breeder flock.
- Old breeders.
- Inbreeding or chromosome abnormalities.
- Nutritional deficiencies.
- Drugs administered to the breeders and/or pesticides toxins.
- Contamination from for example hands when handling eggs, or dirty incubator.

Day 3-6 - Dead embryo

*See causes for day 3
- Inadequate ventilation in the incubator.
- Improper turning of the eggs, or incorrect turning angle.
- Vitamin deficiencies.

Day 7-17 - Dead embryo - embryo will show feather follicles (day 8), feathers (day 11)

- Incorrect incubator temperature, humidity (*Low humidity increases abnormalities of the aortic arches.)
- Incorrect, or infrequent turning of the eggs.
- Inadequate ventilation.
- Contamination of the eggs.
- Nutritional deficiencies.
- Lethal genes in breeders.

Day 18-21 - Dead embryo

- Incorrect incubation temperature, humidity, turning of eggs (during earlier stage of incubation), ventilation.
- Contamination.
- Eggs chilled too severely.
- Nutritional deficiencies.
- Embryonic malposition.
- Embryo failed to switch to lung respiration and other intra-embryonic circulation.
- Hereditary, lethal genes, abnormal chromosomes.
- Twins - double yolk egg development.
- Incubator opened too much during pipping and hatching.
- Poor shell quality.
- Disease in breeder flock.

Full term embryo, did not pip, dead in shell. Eggtopsy shows yolk sac not absorbed, or only partially absorbed. May be some residual albumen (egg white).

- Inadequate turning during incubation, especially during the first week, resulting in decreased embryonic membrane development and nutrient absorption.
- Humidity too high during incubation, or after lockdown.
- Incubator temperature too low, or too high.
- Nutritional deficiencies.
- Hereditary.
- Disease in the breeder flock.
- Eggs stored too long prior to setting.
- Inadequate ventilation.

Full term embryo, pipped, dead in shell.

- Low humidity or temperature for prolonged period.
- Low humidity during hatch.
- Too high temperature during hatch.
- Nutritional deficiencies.
- Disease in breeder flock.
- Inadequate ventilation.
- Inadequate turning off eggs during first 12 days.
- Rough handling of egg, causing embryonic injury.
- Eggs stored too long prior to setting.

Chicks hatching early

- Small eggs (some breed's eggs, for example some bantams tend to hatch a bit earlier than 21 days)
- Incubation temperature too high.
- Incubation humidity too low.

Chicks hatching late

- Larger than normal eggs.
- Eggs from old breeders.
- Eggs stored too long prior to hatching.
- Incubator temperature too low (a single degree (Fahr) can delay the hatch by as much as 24 hours)
- Weak embryos.
- Inbreeding.
- Incubator humidity too high.

"Sticky" chicks - chicks smeared with albumen

- Low incubation temperature.
- High incubation humidity.
- Incorrect or inadequate turning of the eggs, resulting in improper membrane development and function.
- Eggs stored too long prior to setting.
- Overly large eggs.

Chicks stuck in shell, dry, may have fragements of shell stuck to down

- Humidity too low during egg storage, incubation and/or hatching.
- Incorrect or inadequate egg turning during incubation.
- Egg shell cracked or of poor quality.

Further recommended reading: Diagnosing hatch failures - It starts with the egg