The Digestive System of a Chicken

Before reading about digestive system problems in chickens, it is helpful to understand how the digestive system works. Hens don't have teeth of course so the way they digest their food is completely different to mammals.

digestive-system-of-a-chickenThe digestive system of a chicken mechanically and chemically breaks down food and allows nutrients to be absorbed ready for use in the body. It is important to understand how the digestive system works in order to get a better idea of digestive system problems and to know what is normal (like a bulging crop or the caecal discharge). The main problems that we encounter as hobby poultry keepers in the digestive system are worms and crop problems such as impacted crop / sour crop.


Coccidiosis in Backyard Chickens

When we find our birds with loose droppings the first disease that springs to mind is coccidiosis. But what exactly is coccidiosis and how does it affect our birds?

depressed-bird-with-CoccidiaCoccidiosis is a parasite which damages the gut wall of chickens. There are a number of species of coccidiosis and their affects vary from harmless right through to life threatening.
There are six species of Eimeria (coccidiosis) which are generally considered to be significant for chickens: E. tenella, E. brunetti, E. necatrix, E. maxima, E. mitis and E. acervulina. Each of these species prefers to live in and damage a specific region of the gut. For the purposes of treatment and prevention of coccidiosis it is unimportant to ascertain which species is causing disease in your birds and in many cases several species may be working together to cause disease.


Impacted Crop

An Impacted crop is caused by a blockage in the crop. This can be caused by tough stems of woody grass that cannot pass from the crop down into the proventriculus. The crop feels full and feels like dough. Check first thing in the morning before the bird has had a chance to eat to see if the crop has emptied overnight.


Diarrhoea in Backyard Chickens

Alongside respiratory disease- diarrhoea is one of the most common conditions to affect chickens kept on small holdings or in domestic situations such as the back garden.

A normal dropping

The causes of Diarrhoea in Poultry

Before we look at causes of diarrhoea it is worth mentioning that a normal bird dropping should be firm and brown with a white part on the top which is made from urates (the chickens urine) as chickens urinate and defecate in one motion. 

A healthy bird will also pass a caecal dropping every 10th dropping or so, these are usually caramel in colour.


Pendulous Crop

A pendulous crop is when the crop gets blocked and the food stretches the crop so that it hangs down lower than it should do (and often swings 'like a pendulum' as the bird moves around).

pendulous cropWhilst a chicken may be able to live for some time like this and appear to be in no pain, there is damage being done to the muscles in the crop due to the weight of the food and the more food that goes into it, the more it is being stretched so it is best to address the problem sooner than later.


Sour Crop

Sour crop or thrush in chickens is caused by the Candida Albicans yeast in the crop. It can easily be identified by the putrid smell that comes from the bird's mouth.

Sour crop can occur after a course of oral antibiotics (such as Baytril or Tylan) or if there has been a shortage of Vitamin A in the bird's body. It is more common in growers than adult birds.



Coccidiosis is a disease caused by the coccidial protozoan organism, an internal parasite called Eimeria. These live inside the cells that line the birds intestine.

As they reproduce, they cause bleeding and swelling in the intestines. Birds lose a lot of liquid through diarrhoea and cannot absorb nutrients from their food and will soon die if they are left untreated. Coccidiosis normally only infects young birds. Older birds will build up an immunity over time. There are a number of different species of Coccidiosis parasite, some cause a higher mortality rate than others. There are five that can cause death in Chickens, 3 in Ducks, 3 in Geese, 5 in Turkeys, 3 in Pheasants.


Overweight Chickens

Chickens are the most likely candidates to become overweight. Birds that are caged, kept in a small run or are fed the incorrect diet are the most at risk of becoming overweight. Fat hens don't lay eggs, are prone to heat stroke, fatty liver syndrome and can have reproduction problems.


Histomoniasis ‘Blackhead’ in Turkeys

Blackhead is a very old disease of poultry caused by a tiny single celled parasite called Histomonas meleagridis. Blackhead is usually carried by the harmless caecal worm 'Heterakis gallinarum' but it may be transmitted directly between birds.

Once a bird is infected with blackhead the parasite (whether it was carried by the caecal worm or not) it burrows into the wall of the caecum (the blind gut). This burrowing causes ulcers to form in the blind gut and can initially cause bright yellow diarrhoea. The blackhead next burrows through the blind gut and crosses the abdomen into the bird's liver. This causes severe liver damage and can lead affected birds to:


Tapeworms and Fluke in Backyard Fowl

Over the past few years awareness of round worms and gape worms in backyard poultry has increased dramatically with owners either routinely worming with Flubenvet, or using treatment in response to routine worm egg counts to successfully control worms in their backyard flocks.

However we are frequently contacted by owners asking about both tapeworms and flukes in backyard birds.

Tapeworm-SegmentsThere are many different species of tapeworms that can infect backyard poultry. The majority of these species are totally harmless, however large numbers of tapeworms may cause weight loss and loss of egg production. However the impetus to treat tends not to come so much from a concern about the health of the birds but rather from the bird's owners revulsion at the site of these long tapeworms (up to 25cm in length) in their birds' droppings. Tapeworms have an indirect lifecycle meaning they need another organism such as a fly or earthworm in order to complete their lifecycle. (The species of the other host needed will depend on the species of tapeworm).


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