The digestive system in domestic chickens is very simple but efficient when compared to many other species, such as cattle. Having a basic understanding of a chicken’s digestive system is very helpful when it comes to understanding their digestive health. Knowing what’s normal is the key to recognizing abnormalities, which helps to spot symptoms more quickly. Then, you can take the appropriate steps to treat your chook’s digestive issues before it progresses to something more serious. The digestive system is responsible for the ingestion of food, its breakdown into its constituent nutrients, their absorption into the blood stream and the elimination of wastes from this process.
Overview of the Digestive System
A chicken has a digestive tract similar to most birds. A chicken’s beak and mouth is the starting point and because chickens do have not teeth, they use their tongues to push food to the back of their mouth where it travels down the esophagus and into the crop. From the crop (which is a temporary holding tank) food gets sent either to the “true” stomach (proventriculus) or to the gizzard (ventriculus). After food has been munched by the strong muscles of the gizzard, food passes into the small intestine, where nutrients are taken in to the ceca and beneficial bacterial continue to break food particles down. From the ceca, food moves into the large intestine and then exits as droppings through the cloaca.
The Beak and Mouth:
A chicken’s beak is an amazing tool-made of horny skin – the same material as human fingernails, lying over the mandible and incisive bones that serve as the bony foundation of the beak. As with human fingernails – the chicken’s beak needs maintenance - Pecking blocks can come in handy to help maintain perfect beak shape. With no teeth to break down food, a chicken’s mouth starts the whole digestive process with a host of enzymes, before its tongue sends the moist food toward the back of its mouth for swallowing.
Simply put, the oesophagus is basically a long pathway to the stomach. Just like a humans.
Food travels down the esophagus to the crop (which is really just a bulge in the esophagus), where the chicken stores the food until she can digest it at her leisure. The crop has two roles in your chickens health – while it plays an important role in digestion, acting as a sorting bin for food, it also stores leftover bits of feed for the chicken to enjoy later. A chicken can peck more food than it needs at any given time because its crop will store any excess food for when they need it most.
The crop acts as a director of sorts, sending food to either the stomach or to the gizzard. A chicken’s stomach breaks down easy to digest food, whereas, more troublesome complex foods such as long grains and fibrous materials are sent to the gizzard where grit helps to break these down.
The Stomach (Proventriculus):
The Proventriculus, or “true” stomach, is really where the real digestive action begins. Abundant amounts of hydrochloric acid and digestive enzymes work together to mash and further break down food. The food still hasn’t been ‘chewed’, though.
The Gizzard (Ventriculus):
The Ventriculus or gizzard is where more complex food is thoroughly ground up. The gizzard is home to strong muscles whose job is to further grind up the already mashed up food sent from the stomach or to break down long grains and grasses and fibrous materials that the typical backyard flock pecks up during free-range time. Vigorous muscle contractions work together with little stones to crush food into tiny pieces – acting as the bird’s teeth. Fortunately, chickens who free-range regularly typically ingest enough stone matter to aid the gizzard’s digestive processes.
The Intestinal tract:
Chickens have a pancreas, liver, and intestines, which pretty much do the same things as they do in humans. The digestive tract layout differs, though, when you get to the cecum. The plural of cecum is ceca, which is useful to know, because birds have two. The ceca are blind pouches located where the small and large intestines come together.
These two small glands located off the large intestine use bacteria to ferment any undigested material. Birds extract a little extra nutrition out of their meal, especially fatty acids and B vitamins, through the fermentation process that happens in the ceca.
The Large Intestine:
The Large Intestine absorbs water and removes unnecessary waste products.
The Kidneys, Cloaca and Vent:
The Cloaca is a small area located just inside a chicken’s vent area where digestive system wastes combine with a chicken’s urinary wastes or urates and exit through the vent. Chickens don’t urinate, and they don’t have a bladder. Urinary system wastes (urates is the word used for bird urine) produced by the kidneys are simply dumped in with the digestive wastes at the end of the digestive system, at the cloaca, or vent. That’s why normal chicken droppings contain white urates mixed with darker digested material.
Common Causes of Digestive Distress:
A chicken’s digestive system is a highly tuned food processing machine. However, from time to time your chooks may experience digestive distress. The two most common culprits responsible for digestive distress in chickens are worms and crop malfunctions. Though even a mild worm infestation can wreak havoc in your flock, worms are easily preventable and easily treated should they make their way into your flock (typically from wild birds or ducks interacting with your flock). Crop malfunctions on the other hand, can become serious if not diagnosed early. If in your attempt to treat a potential crop problem, you do not see improvement in a day or two, always seek the advice of a veterinarian as soon as possible.