If you keep chickens, chances are you’ve seen a soft shell egg. There are several reasons why this can happen, and you should not worry at all. But why do chickens lay soft shell eggs? How can you prevent it from happening?
Let’s dive into the world of eggshells and figure out what’s going on.
- What are soft shell eggs
- What causes soft shell eggs
- Reasons chickens lay soft shell eggs
- How to stop chickens from laying soft shell eggs
- Is it safe to eat soft shell eggs
What are Soft Shell eggs?
Soft shell eggs are normal eggs with a very thin shell or no shell at all. If the shell is missing, the membrane keeps them together. The eggs are very fragile and sometimes crack in the chicken’s body.
The thin calcium-deficient shells are easily cracked with your fingers. When there is no shell, the eggs feel like little water balloons. However, they usually don’t survive long, and you find them broken in the nesting boxes or at random places in the run or coop.
What causes Soft Shell eggs?
Soft shell eggs are caused by quirks in the eggshell-building process. It takes about 20 hours for a shell to develop in the shell gland. If there is a lack of calcium, a shell-gland problem, or the egg leaves the gland too quickly, the result is a soft-shelled egg.
In total, it takes about 24 hours to form a whole egg. Chickens have many tiny yolks in their ovary, ready to develop.
When a yolk starts its journey, it passes through the magnum, where the egg whites are developed. Then they move to the isthmus, where the shell membrane forms. When they arrive in the shell gland or uterus, the eggshell is created. From that point, it takes about twenty hours before the egg is laid through the vent.
In the case of a soft-shelled egg, everything in the process goes well up until the shell formation in the shell gland. Sometimes there is not enough material, like calcium, to build the shell. Sometimes a medical condition prevents the shell gland from doing its work properly. And sometimes, the egg is pushed out too quickly, which doesn’t give the egg enough time to develop a proper shell.
Let’s make this more concrete and look at the top reasons you end up with a soft shell egg.
Reasons Chickens lay Soft Shell eggs
There are several reasons why chickens lay soft-shelled eggs. When multiple flock members lay soft shells, it’s probably an external reason the flock is dealing with, like hot weather or a stressful situation.
If it’s only a single hen in the flock laying soft shells, there is probably something going on with her. It doesn’t always have to be a medical condition. It can also be that she just started laying.
The pullet just started laying eggs
It’s very common for young birds to start with smaller, thin-shelled eggs. It’s certainly nothing to worry about and will resolve after a couple of eggs.
When young pullets start to lay their first eggs, the egg production machinery is activated. Laying an egg is very demanding for the chicken’s body, and it’s a complex biomechanical system. Hens can not get all the calcium for the eggshell out of their food. That’s why they have extra reservoirs of calcium in their skeleton.
Some bones, like the thigh bone (femur) and the shank bone (tibia), can store extra calcium in bone tissue. The bones in their wings and toes also have this special bone tissue on their surface. These bones are called medullary bones. Chickens mobilize almost half of the calcium in their bones to add to the dietary calcium. Without the extra calcium from the medullary bones, a chicken lays eggs with fragile and weak shells.
In young chickens with a lighter skeleton, all these processes are firing up to produce their first eggs. So make sure they switch to layer feed in time and that they have access to calcium sources. Switching the birds to layer feed three weeks before their first egg allows them to build up some calcium reserves in their skeleton.
An eggshell is made almost entirely out of calcium carbonate crystals. Chickens get the necessary calcium from their food and their medullary bones. When layer hens mature, they mobilize 47 percent of their body’s skeleton calcium to make an eggshell.
The egg stays 20 hours in the shell gland to form the crystals, but if there is no calcium, the shell can’t form. Ensure laying hens have access to layer feed and extra calcium sources like oyster shells.
Stress is one of the major causes of delayed egg-laying and eggshell abnormalities. If the chicken undergoes any form of stress before the yolks reach the shell gland (where the eggshell forms), the entire shell formation is affected, which results in soft-shelled eggs.
The higher the stress levels and the longer it takes, the more abnormal the deformities and the more thin-shelled eggs. The stress disturbs the egg production processes and can simultaneously accelerate egg laying. Stress can even switch a chicken to survival mode and completely shut down the egg laying.
There are multiple reasons why chickens can have stress. Common examples include:
- when they move to a new chicken coop or when they are added to a new flock
- when there is not enough space, use our chicken run size calculator to see if your chickens have enough wiggling room
- when there is an eager or aggressive rooster or when there are not enough hens for every rooster
- when there is bullying and pecking going on
- when they are living in shady confinement conditions or chicken coops lacking the correct infrastructure
- when there has been an attack of a predator
- when there is a red mite manifestation
- when the chicken has a viral or bacterial infection
The link is so strong that the poultry industry counts the number of abnormal eggs to get an indication of the stress levels their chickens are suffering.
It’s too warm
A very specific reason for thin-shelled eggs is heat stress. Apart from the stress hormones, the heat comes with high ambient temperatures that interfere with the chicken’s body processes.
One example is the calcium-binding protein calbindin-D28k, an essential protein for eggshell building. When temperatures are high, the protein is missing in the eggshell gland and can’t do it’s job properly. Coop temperatures above 80 degrees Fahrenheit (30C) negatively affect eggshell thickness and density. In general, heat stress decreases the amount of circulating ionic calcium in the chicken’s blood.
The heat typically affects multiple members of the flock. When the ventilation of the coop is not up to par to cope with the heat, the air quality can drop drastically due to ammonia fumes. Bacteria in the chicken’s droppings break down nitrogen to generate toxic gases with a pungent odor. This can irritate the birds, give them stress and irritate their eyes, sometimes with foamy bubbles.
When you live in an area with hot summers, make sure to:
- have appropriate ventilation in your chicken coop
- provide shelter and shades in the chicken run
- use systems to cool down your chickens when it gets too hot
Thin-shelled eggs can be an outcome of disease too. When the chicken’s body fights disease, other less survival-critical biological processes are scaled down. In severe conditions, the hen can even stop laying eggs. The energy in the chicken’s body goes to the immune system for survival.
Diseases also directly impact the body processes and can interfere with the hen’s ability to lay proper eggs. Some diseases will directly impact the egg machinery of a chicken:
- Avian Osteoporosis – also called Cage Layer Fatigue, is a common condition in laying hens. Chickens show progressive loss of structural bone tissue. This is especially apparent in the laying period due to the fact that the body uses so much calcium from the medullary bones. This results in fractures and structural bone loss, thin eggshells, sometimes deformed legs, and difficulty standing.
- Egg Drop Syndrome – a viral disease that targets laying hens. The adenovirus causing the Egg Drop Syndrom is coming from ducks and geese. It was probably transmitted to chickens with contaminated vaccines. When infected, the eggs will change in color first. Then, chickens will lay smaller thin-shelled, soft-shelled, or shell-less eggs.
- Egg Yolk Peritonitis – a condition that occurs when the eggshell gets ruptured, and the yolk is moving freely within the body cavities of the bird. This condition goes hand in hand with secondary infections and can result in multiple soft thin-shelled or shell-less eggs.
Other diseases can indirectly impact eggshell production, and the link might not always be that obvious.
One such example is Infectious Bronchitis, a common respiratory disease caused by the coronavirus.
Bronchitis influences the chemicals that are produced in the Magnum, the organ where the egg whites form around the yolks. This results in distorted egg membranes, which eventually disrupts eggshell mineralization. The end result is a thin distorted, body-checked, or corrugated eggshell.
Following other diseases can result in thin eggshells:
- Avian Intestinal Spirochetosis: an intestinal disease caused by a bacterial infection. Hens lay smaller eggs with pale yolks and thin, poor eggshells.
- Defective Shell Gland: the eggshell develops in the shell gland, so an undeveloped shell gland or any shell gland condition will directly impact the eggshell.
- Salpingitis: an inflammation of the oviduct, usually due to a bacterial infection from the vent (cloaca), often results in malformed eggs with thin eggshells
- Ornithobacteriosis: a bacterial infection that can result in smaller, deformed, or thin-shelled eggs.
- Avian Influenza: a global contagious viral infection that can affect the respiratory tract and multiple organs.
- Chronic Respiratory Disease: or mycoplasmosis is a common upper respiratory disease.
- Ochratoxicosis: poisoning with mycotoxins generated by fungi, a common contamination seen in commercial feed.
- Ovarian Tumors: unfortunately cancerous ovarian tumors are common in chickens. So common that they are used to research ovarian cancers in humans.
- Newcastle Disease: Newcastle Disease is a global viral disease with terrible symptoms such as twisted neck and wing paralysis
A disease that gets its own chapter is the Egg Drop Syndrom.
Vitamin D is a fat-soluble vitamin that plays a prominent role in calcium processing. It’s an essential vitamin for growth, bone health, and eggshell formation.
When chickens lack vitamin D, they will lay fewer, smaller, deformed eggs with thin shells. With severe deficiencies, inadequate calcium levels can cause softening of the beak and deformities of the legs. Chronic deficiencies result in lower bone mineral densities and an increased risk of osteoporosis.
There are several forms of vitamin D. For egg-laying and calcium processing vitamin D3 is the most important. It plays a vital role in the growth of chicks and the egg laying of hens.
Chickens get vitamin D3 in two ways:
- by direct sunlight, where it is photochemically synthesized from ultraviolet light
- via the diet and optional vitamin D3 supplementation
Sunbeams that travel through the glass in windows are filtered and lack the needed ultraviolet light.
When adding supplements to the diet, it’s important not to exceed the daily recommendations. Adult laying hens should be somewhere around 3500IU/kg of vitamin D3. Overdosing vitamin D3 can lead to calcium excesses in the bloodstream, resulting in hypercalcemia. This can result in heart problems and liver issues.
Manganese is an essential dietary nutrient for chickens. It’s a coenzyme in the biological processes of bone and eggshell formation. It’s also a vital nutrient in the operation of several proteins. Manganese deficiency results in thin, deformed, or soft shell eggs and can lead to parrot beaks in growing chicks.
The current guidelines recommend 60mg/kg of manganese for laying hens and broilers. Diets often contain much more manganese than the daily recommendation, and deficiencies are rather rare. Some people believe adding Manganese will aid in egg laying. Scientific studies concluded that adding supplementation up to 200mg/kg did not improve egg laying performance. However, there might be a difference between organic and inorganic supplements. In some cases, it seems that increasing to 90mg/kg can improve the eggshell quality and thickness.
Genetics of Egg Layers
With selective breeding, some chicken breeds like the Leghorn are turned into egg-laying machines that produce over 300 eggs per year. The birds are genetically selected for their egg-laying qualities and not for the thickness of their eggshells.
In some fast layers, the total time from egg yolk to laying is drastically reduced. When the egg doesn’t stay long in the shell gland, the resulting shell will be thinner. Sometimes the eggs come so fast that the hens lay two eggs in a single day.
Due to genetics, some fast-laying hens are predisposed to laying soft-shelled eggs.
Age and Laying periods
When hens get older, their egg-laying machinery is slowly deactivated. There will be fewer eggs, with thinner shells and a higher chance of soft-shell eggs. The metabolism is slowing down. Fast egg layers can’t mobilize enough calcium from their medullary bones to create strong eggshells.
The chances of getting soft-shell eggs are higher the older the hens get. The shell structure and thickness will deteriorate slowly over time due to age-related changes. Eventually, the hen will stop laying.
The same holds true when the hen is approaching the end of a laying period. The complete process of shell formation spread over a full laying year is biologically a stressful event. When the end of the laying period approaches, eggshell quality declines, which can result in thin shells or soft-shelled eggs.
Diet and Overweight Chickens
Chickens should get enough nutrients in their diet that aid in shell-forming. Sufficient calcium and vitamin D3 are crucial elements. But other vitamins and minerals, like vitamin C and phosphorus, also play a role in the metabolism.
Feeding chickens with kitchen scraps can seem like a good idea but often leads to a shortage of vital micronutrients. Some feed, like wheat, doesn’t contain sufficient amounts of protein for laying hens. And other feed, like maize, can cause your hens to build up internal fat surrounding the organs.
Overweight chickens that carry too much fat will produce fewer and lower-quality eggs. Sometimes these eggs are thin-shelled or have no shell at all.
If a thick layer of skin covers your chicken’s breastbone, it might have weight issues. Prefer balanced layer feeds, limit the number of treats and corn and let the birds free-range if possible.
Chickens live by the light. When the days get longer, they are up all day. During the year, they get various amounts of sunlight depending on the day’s length.
In poultry science, this is called the photoperiod. It’s the amount of time during which the chickens get some daylight. A lot of times, the days are artificially prolonged to increase egg production.
The photoperiod has a significant influence on the egg quality and eggshell thickness. The light regulates important hormones of the chicken that play a crucial role in egg development. The luteinizing hormone (LH) and follicle-stimulating hormone (FSH) regulate the essential processes in the oviduct and follicle. Estrogen activates the reproductive system and is regulated by light.
Short-day light can decrease egg production and egg quality, increasing the chances of soft-shelled eggs and thin eggs. Artificial light is widely used in poultry to counter short days and increase egg production. The results suggest that a minimum of 13 hours of light is needed for optimal egg production. Eggshell quality and production are optimal when chickens receive 14 to 18 hours of natural light daily.
How do I stop my chickens from laying soft-shelled eggs?
To prevent chickens from laying soft-shelled eggs, ensure they are stress-free, have a proper diet, have enjoyable ambient temperatures, enough daylight, and are healthy and free from any diseases.
- provide your flock with a diet that contains calcium, phosphorus, manganese, and essential micronutrients. Limit the number of treats.
- ensure they have appropriate housing conditions and enough space in the coop and run; prefer free ranging over confinement
- protect your chickens from predators, any attack or luring predators can bring a lot of stress
- avoid social stress in the flock by separating bullies and overly eager or aggressive roosters
- ensure the chicken coop has proper ventilation to bring in fresh air
- give your chickens enough light during the day; prefer proper daylight over artificial light
- provide plenty of shade and cool down your chickens during hot summers
Is it safe to eat a soft shell egg?
No, it’s not safe to eat a soft-shelled egg. The eggshell and the natural bloom coating protect against the infiltration of bacteria from the dirt, feces, and blood. Eating soft-shelled eggs can result in food poisoning, salmonella infections, nausea, vomiting, and diarrhea.
Even removing the protective bloom that covers the eggshell is not recommended. It’s a natural barrier that prevents bacteria and toxins from entering the eggshell. That’s why you don’t need to wash eggs before storing them, only before eating them.
Soft-shelled eggs are common and not necessarily a problem. When chickens start laying, or when they are approaching the end of a laying period, they sometimes just produce thin-shelled or soft-shelled eggs.
The eggshell forms in the shell gland of a chicken. The calcium to create the shell comes from the chicken’s diet as well as their medullary bones. The medullary bones are skeleton bones that can store calcium reserves.
Thin shells and soft shells occur when there is either an issue with the shell gland, insufficient material to form the shell, or when the egg passes too fast so the shell can’t form.
These conditions can be caused by malnutrition, any kind of stress, heat, lack of daylight, diseases, or health issues in general. Some diseases like Egg Drop Syndrome or Avian Osteoporosis directly impact the shell formation process. Other diseases like Infectious Bronchitis can have a rather indirect effect.