Case Study: Internal Layer

Internal Laying

Internal laying is a condition in which a hen lays eggs internally instead of how they are normally laid- externally. It may be caused by a genetic congenital defect or acquired as a result of an infection or trauma to the oviduct.

In normal egg production the yolk travels from the ovary to the cloaca (vent) where it is laid outside the body. In the roughly 24 hours that journey takes it is covered by the white (albumen), membranes and shell. If a hen has sustained damage to her oviduct the egg doesn’t form normally and the yolk is laid into the abdomen. In these hens, partially or fully formed eggs can be found in the abdominal cavity.

Thin-shelled or soft-shelled eggs can break internally as well. The yolks may be absorbed over time, but in most cases the hen produces them faster than they can be absorbed resulting in a build-up within the abdomen. The egg yolk is a rich medium for bacteria to grow, which increases the hen’s risk of bacterial infections (i.e. E.coli).  Eventually, all the rotting egg material inside of the hen’s body will begin to exert pressure on her internal organs, restricting her ability to breathe properly and can lead to Salpingitis and Egg Yolk Peritonitis.  In an effort to alleviate the pressure she will assume an upright stance.

Interpreting DIY necropsy photos are not my forte. I often send them to my online friend, Deb, who is a Veterinary Technician for her opinion. In this case, it’s her hen that died and she’s sending the material to me. Here’s her story:

Gracie , Black Copper Marans Hen, 4 years old

“Her eggs were normal when she first started laying. Later they started having blood spots here and there, which increased in frequency to the point where I started pulling her eggs from those I was giving away. Towards the end, the eggs became very thin shelled – when I collected them from the nest box, they’d break open with the tiniest pressure. She stopped laying 4-6 months before her death.

I knew Gracie had an egg lodged somewhere in her abdomen. I inserted my finger in her vent thinking she was egg bound and could feel the egg through a wall of skin. If the skin wasn’t surrounding it, I could have gotten it out.

The egg was there for at least 5-6 months. I know the prognosis isn’t a long life when they have a retained egg, but it wasn’t coming out without surgery.  I figured that was too risky and there are no real Avian Vets in my area. The egg was somehow surrounded by membrane as if her oviduct inverted itself, prior to the abdomen growing hard and enlarged within her last month.

Gracie stayed with the flock, was the first to the feed when I opened the coop door, slept in a nest box with a couple of other hens who seemed to cuddle her on cold nights, and cooed like no other chicken when getting settled for the night. We’d chat every evening. She was cooing last night and I figured I’d see her in the morning, but she died overnight in her nest box.

I necropsied her and took photos as I was peeling away the membranes.

Interesting that when I cut through into her abdomen, there seemed to be more membrane layers than normal. Each picture was taken after cutting through a thin membrane.

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Her liver looked quite small compared to other birds I’ve necropsied. I thought the lungs were kind of small, but maybe they were normal.

I’m surprised I don’t have a picture of the crop contents, which was full of crumbles and scratch.

I would love to figure out how Gracie’s egg ended up in a position where I was unable to remove it when she became egg bound. It was frustrating that I could feel the egg, but it was not moveable through a membrane wall. I’ve had other egg bound hens and never came across this scenario.”

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I sent some of Gracie’s necropsy photos to a board certified Avian Veterinary Pathologist in the USA and she concurred with the diagnosis:

“Good necropsy photos – organs presented in situ. This is an internal layer, which is usually caused by some type of trauma to the oviduct, but there are other causes. It results in reverse peristalsis of the oviduct so eggs are ejected internally and also stuck in the oviduct in various stages of laying.”

Many thanks to Debra Watt for sharing her story and photos, used with permission.