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Egg Peritonitis

The Chicken Vet is commonly asked about egg laying problems and chickens laying soft shelled eggs. Sometimes these queries are nothing to worry about as your chickens are just going through a normal process of coming into or going out of lay. However, there are occasionally difficulties and these birds may be experiencing an internal or blind layer problem. These terms are used to describe birds whose oviducts (egg tubes) are not functioning as they should be.

Usually the oviducts carry the yolk from the ovary to the vent over a 24 hour period. During this time the white, membranes and shell are formed around the yolk. In chickens with damage to their oviducts the egg does not form properly and the yolk is laid internally into the belly/abdomen. These yolks can be absorbed over time but in most cases the chicken lays them internally faster than they can be absorbed resulting in a build up within the abdomen. This enlarges the abdomen and causes the chicken to experience discomfort and difficulty breathing. In order to help relieve the pressure on the abdomen the chickens adopt an upright penguin-like stance.

Post mortem with an
abdomen containing pussy yolks

Some factors such as coming into lay and stress can cause the odd internally laid egg.  However, severe oviduct damage, can lead to permanent oviduct problems and therfore they remain internal layers for life.

This condition leads to a life of discomfort. Often the chicken will lose weight and have prominent breastbones. Deceivingly, due to the build up of egg yolk in their abdomens, they appear to be roughly a normal weight. 

These birds can be

  • speyed (have the oviduct surgically removed)
  • have a hormonal implant inserted by a vet to stop ovulation
  •  kept by a watchful and observant owner who knows the problem exists and makes veterinary contact if they suspect a brewing peritonitis


  • unfortunately, in some cases the most humane option is to put the bird to sleep. 

The picture shows a post mortem with an abdomen containing pussy yolks.

The mass of egg yolk in the abdomen can provide a rich medium for bacteria such as E. coli to thrive and cause peritonitis. These birds become dull with hot swollen abdomens and in severe cases they will develop blood poisoning and go into shock and invariably die.

Treatment often involves using antibiotics which usually helps to treat infection, however, unless you are able to stop the bird laying internally, the peritonitis will usually return.


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Eggshell Quality

Eggs are remarkable objects, from a good source of food right through to an incubation chamber.  The eggshell and membrane hold the content of the egg, protect the egg from damage, and helps keep out bacteria.  Keeping out bacteria is very important for our health and the health of any developing chicks.  

It takes approximately 20 hours for a shell to form around the membranes. It is made up of a protein scaffold mixed with calcium carbonate crystals making up approximately 96% of the shell. The shell is deposited onto the membranes (along with pigment) in a region of the oviduct called the eggshell gland. The cells lining this gland are very similar to the cells lining the trachea (windpipe) and the kidney. This means that respiratory diseases such as Infectious Bronchitis, which attack the respiratory tract, can cause damage to the eggshell gland in the oviduct resulting in poor shell quality and lack of pigment i.e. a hen that normally lays brown eggs will lay pale/white shelled eggs.

There are a number of causes of pale/poorly shelled eggs:

  1. Respiratory Diseases (IB, Newcastle Disease, Avian RhinoTracheitits virus/ART, Mycoplasma) can damage the egg shell gland causing poor shell quality. This is the most common cause of pale eggs and poor egg shells. If your chickens have abnormal shells then look closely for signs of Respiratory Disease. Most of these diseases are viral and antibiotics may have a limited effect on the problem. The birds may recover but a full return to their former glory cannot be guaranteed.  If you want to determine which disease has cuased the problem then a blood test can be carried out. If you have a large flock you may wish to vaccinate.
  2. Bright sunlight in the summer can cause pale shelled eggs, however the exact reason for this phenomenon is still widely unknown. Keeping birds enclosed for several days can reverse this.
  3. Laying cycles - chickens coming into or out of lay will take a few days before their oviducts start to function properly causing poor quality abnormal shells. This can lead to thin shelled eggs. Furthermore, as the bird goes through her cycle, her oviduct loses its tone leading to oddly shaped eggs.
  4. Calcium or vitamin D3 deficiency can cause poor shell quality but this is rare. If the birds are on a good diet with some crushed oyster shell they should not have diet related egg shell problems. However, if you suspect that this is the problem then you can supplement the birds with vitamin D3.
  5. Stress can cause abnormal egg shells. If the bird is stressed (e.g. due to a predator attack), then the egg’s passage through the oviduct can be halted and extra shell can be added sometimes causing a ridged waist.
  6. Genetics - bear in mind that genetics can give a variety of shell colours from green shelled Legbar eggs to brown speckled Maran eggs to white shelled Leghorn eggs.



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Egg Hygiene

We all like to tuck into a nice freshly laid egg whether it’s scrambled, fried or poached. Whilst eggs are a fast, safe and healthy food it is worthwhile taking a few precautions to protect you and your family.

The main concern with eggs is normally in relation to Salmonella. However, the surface of a contaminated egg may contain other harmful bacteria. The first important way to maintain clean, safe eggs is to keep your chickens in a clean environment. This means making sure they have access to fresh food and water which is replaced daily.

Feeders and drinkers should be regularly cleaned and disinfected using Rhodasept. Ensure your chicken house is cleaned and disinfected regularly and your chicken run is kept clean and mud free where possible (bark can help).

Rodents and wild birds can carry several diseases that can infect both you and your chickens. Never feed your chickens outside and keep all feed in a secure place with no access for wild birds and rodents. Keep grass and weeds around your chicken house and run cut down, as long vegetation provides the perfect place for vermin to hide. Change the bedding in your nest boxes weekly to ensure that the eggs are laid onto a clean surface.

Any dirty eggs are unsuitable for human consumption, or hatching for that matter!

Always ensure you keep your own hands clean and wash them after handling the chickens or collecting eggs each day. We recommend Intersoft N for this purpose.

Never be tempted to wash dirty eggs as this will spread the bacteria around the shell. Even clean eggs should not be washed as they are coated in a waterproof cuticle which protects them from bacteria entering in through the tiny pores on the surface of the egg shell. Washing eggs removes this protective cuticle.

Ideally, eggs should be stored in a cool place such as your larder and not in your fridge.

Always use eggs within three weeks of being laid. You can use a pencil to mark the date once they have been laid.

Finally, always ensure your eggs are cooked properly before eating them.


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We frequently get calls from concerned owners about the risks of getting Salmonella from their chickens and eggs.

What exactly is Salmonella?

Salmonella is a bacteria which can infect both animals and man. There are many species of Salmonella, all of which have a preffered animal to infect, for example, Salmonell Dublin prefers to live in cattle. Not all Salmonella cause illness and not all Salmonella which causes disease in one animal will go on to cause disease in another. But whilst most Salmonella nellaspecies prefer to infect a particular type of animal they can infect other animals and humans.  For example, Salmonella nella Enteritidis prefers to infect chickens but causes no problems for them.  However, it can occasionally go on to infect people causing vomiting and diarrhoea.

What are the signs of Salmonella?

Salmonella can cause vomiting and diarrhoea in people and in extreme cases, causes blood poisoning. In animals it can cause diarrhoea and blood poisoning.

Can Salmonella cause illness in my chickens?

Yes, it is indeed possible for Salmonella to cause disease in chickens; however this is extremely rare. There are two main species involved: S. Pullorum and S. Gallinarum. S. Pullorum can cause blood poisoning, diarrhoea and sudden death in young chicks (under three weeks of age). S. Gallinarum can cause sudden death, diarrhoea and difficulty breathing.

Can chickens carry Salmonella species which can cause illness in me and my family?

Whilst it is not particularly common, Salmonella can cause illness in people, especially if they are vulnerable, such as people with HIV and pregnant women.

There are two species of Salmonella which chickens can carry which can cause illness in people S. Enteritidis and S. Typhimurium. These species do not cause illness in chickens but can in extreme cases infect people. In the 1980’s Edwina Currie caused a storm by claiming that most UK eggs had Salmonella. This caused a plummet in egg sales and subsequently the egg industry began to routinely test all egg and meat producing chickens regularly. Most laying flocks are now vaccinated for these strains of Salmonella.

How do people get Salmonella from their birds?

Most people contract the bacteria from not washing their hands properly after handling their birds or after handling raw meat.

How can I reduce the risk of Salmonella in my birds?

Rodents and wild birds are potential carriers so ensure you control rats with bait stations and keep feed in secure containers.

Use Beryl’s Friendly Bacteria - the 200 friendly bacteria in this product compete for space in the gut with harmful bacteria such as Salmonella.

Chicken Vet Digesti-Health can be given daily in feed to help exclude Salmonella as it binds to the bacteria stopping it attaching to your chickens intestine.

Do I need to vaccinate my birds?

There is no real need to vaccinate your birds provided that you wash your hands properly after handling your chickens and that you cook your food properly.

If you do wish to vaccinate your chickens then it will involve giving your birds two injections 4 weeks apart followed by an annual booster. The problem is that vaccination only protects against Enteritidis and Typhimurium and not all the other potential strains out there.

Can I test my birds?

You can certainly test your birds for Salmonella with a faecal sample. Purchase testing kits in our shop but clearly state you require testing for Salmonella.

If I wish to sell my eggs do I need to test my chickens for Salmonella?

If you have less than 50 birds you can sell eggs at your gate or locally door to door.

However if you sell eggs to someone who will sell them on, such as a shopkeeper, hotelier etc, you need to register with the Egg Marketing Inspectorate.

For more details see the DEFRA website.


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