Inside the Chicken Digestive System: A Complete Guide for Optimal Poultry Health

THE DIGESTIVE SYSTEM OF CHICKEN

the digestive system of Chicken is simple and efficient which helps them get nutrients from food quickly. This is important for their fast growth, high energy needs and, for hens, producing eggs. Unlike cows, chickens don’t have complex stomachs to break down tough plants. Instead, their bodies are designed to absorb nutrients well. To stay healthy and productive, chickens need a diet with high-quality, easy-to-digest ingredients. Breaking down carbohydrates, fats and proteins helps chickens grow strong and stay active.

 

PARTS OF CHICKEN DIGESTIVE SYSTEM 

 

The main parts of a chicken’s digestive system are as follows:

Mouth: Chickens don’t have teeth, so they use their beaks to peck and tear food. Saliva helps moisten the food.

Esophagus (Gullet): This tube moves food from the mouth to the crop and stomach.

Crop: The crop stores food temporarily and softens it. It allows chickens to eat large amounts and digest them later.

Stomach:

-Provetriculus: The proventriculus is the glandular stomach that secretes enzymes and acids for chemical digestion.

–Gizzard: The gizzard grinds food with its strong, muscular structure. Chickens often swallow small stones or grit to help the gizzard mechanically grind food.

Small Intestine:

–Duodenum: The duodenum is the first part of the small intestine, where bile and enzymes break down fats and nutrients.

– Jejunum and Ileum: Further sections of the small intestine, where nutrient absorption occurs.

Pancreas: Produces digestive enzymes and hormones like insulin, assisting in breaking down carbohydrates, fats, and proteins.

Liver: Produces bile to aid fat digestion and processes nutrients absorbed by the intestine.

Large Intestine: Absorbs water and electrolytes from the remaining indigestible food.

Caeca(ceca): The caeca are two pouches between the small and large intestine where bacterial fermentation of undigested food occurs

Cloaca: The cloaca collects and excretes fecal and urinary waste at the end of the digestive system. It also serves a role in reproduction.

Vent: The external opening expels waste

The crop, proventriculus, and gizzard in chickens work together to break down food before nutrient absorption in the intestines. They adapt this setup to their varied diet and rapid consumption.

 

MOUTH

 

• Beak:
  • Shape: The beak is cone-shaped and slightly curved to help chickens pick up food easily.
  • Functions:
    • Food Collection: The beak helps chickens gather and eat food. Since chickens don’t have teeth, they use their beaks to break food into smaller pieces.
    • Preening: Chickens use their beaks to clean and oil their feathers.
• Tongue:
  • The tongue and beak work together to move food into the right spot for swallowing.
• Salivary Glands:
  • The mouth has glands that make saliva, which moistens food, making it easier to swallow.
  • Saliva contains an enzyme called amylase that begins to digest carbohydrates (like starch) right in the mouth.
  • pH of Saliva: Saliva is slightly neutral, with a pH of 7-7.5.
• Palate:
  • Chickens have a hard palate (roof of the mouth) with a small slit that connects to the nose.
• Papillae:
  • Five rows of small, cone-shaped bumps point backward on the palate. These help push food toward the throat.
• No Teeth or Cheeks:
  • Chickens don’t have teeth or cheeks. Instead, their hard, horn-like beak helps them eat.
• Egg Tooth:
  • Baby chicks have a small “egg tooth” on the tip of their beak. It helps them break out of the egg and fall off soon after hatching.

Summary:

The chicken’s beak is a tool for gathering food and moving it to the throat, where saliva starts breaking down the food.

 

CROP

 

• What is the Crop?
  • The crop is a pouch in the chicken’s neck that holds food and water before digestion starts. It helps chickens store food since they don’t have teeth to chew.
• Main Functions of the Crop:
  • Food Storage: The crop holds food and water until it’s ready to move into the digestive system.
  • Moistening and Softening: Saliva makes the food wet and soft, but only a little digestion happens here.
  • Hunger Signaling: When the crop is empty, it sends a signal to the brain to make the chicken feel hungry.
• Safety Adaptation:
  • The crop lets chickens eat quickly and then move somewhere safe to digest. This helps them avoid predators while eating.
• Crop Impaction:
  • If a chicken overeats after not having food for a while, food can get stuck in the crop. This is called “crop impaction.” It can make digestion difficult and cause the chicken discomfort.
• pH of the Crop:
  • The crop has a mildly acidic pH of about 5.5, which helps soften food but doesn’t break it down much.

Summary of the Crop’s Role:

• Location: It’s an out-pocket of the esophagus in the neck.
• Primary Role: To store food and water temporarily.
• Other Roles: Saliva in the crop moistens food, and an empty crop signals hunger to the brain.
• Special Advantage: Allows chickens to eat quickly and safely digest food later.
• Common Problem: Crop impaction can happen if food gets stuck from overeating.

 

ESOPHAGUS

 

• What is the Esophagus?
  • The esophagus is a tube in the chicken’s throat that moves food from the beak to the crop and then to the stomach. It’s a key part of their digestive system.
• Structure:
  • It’s a muscular tube that connects the mouth to the crop, where food is stored and softened.
• Functions of the Esophagus:
  • Food Transport: The esophagus quickly moves food from the mouth to the crop, where it’s stored and moistened.
  • Storage and Soaking: In the crop, food is stored and soaked with saliva to make it softer.
  • Mucus Secretion: The esophagus releases mucus that coats the food, making it easier to slide down into the crop and stomach.
  • Regulation of Food Flow: Muscles in the esophagus control how food moves to the crop and then to the stomach, helping digestion go smoothly.
  • Protection: The esophagus is built to handle sharp or rough food without getting damaged.
• pH Level:
  • The esophagus has a neutral pH (around 7), which protects its lining and helps food move easily.

Summary:

• Role: The esophagus transports food from the beak to the crop and then to the stomach.
• Key Functions: It stores and softens food in the crop, and mucus helps the food slide down smoothly.
• Important for Health: Knowing how the esophagus works helps us understand how to keep chickens healthy and well-fed.

 

STOMACH

 

Chicken’s Digestive System, A chicken’s stomach has two main parts, each with a special job to help break down food so the chicken can get nutrients.

Proventriculus (Glandular Stomach)

• Location: Just before the gizzard in the digestive system.
• Structure: This is a small, tube-shaped organ with several layers.
  • Outer Layer: Protects the stomach.
  • Muscle Layers: Help push food through.
  • Areolar Tissue: Has blood and lymph vessels to help with digestion.
  • Glands: Make digestive juices.
• Function: The proventriculus releases acids and enzymes that start breaking down food. The inside is very acidic, which helps break down food properly.

Gizzard (Muscular Stomach)

• Location: Right after the proventriculus.
• Structure: A strong, muscular organ with thick walls.
• Function: The gizzard grinds food using small stones the chicken swallows. It mixes the food with digestive juices, which helps break it down even more.

Summary:

The chicken’s stomach has two important parts:

• Proventriculus: Adds acids and enzymes to start digesting the food.
• Gizzard: Grinds food, and mixes it with stones and digestive juices.

These two organs work together to help the chicken digest its food and get the nutrients it needs to grow and stay healthy.

PANCREAS

Location:

• The pancreas is a long, thin gland found near the small intestine (called the duodenum) and the liver. It often sits in a loop formed by the duodenum.

Structure:

• The pancreas has two main parts:
  • Acinar Cells: These cells make digestive enzymes that help break down food.
  • Islets of Langerhans: These cells produce hormones that help control blood sugar levels.

Functions of the Pancreas:

• Exocrine Function (Digestion):
  • Digestive Enzymes: The pancreas creates enzymes like:
    • Amylase: Breaks down starch (a type of carbohydrate).
    • Lipase: Breaks down fat.
    • Proteases: Breaks down protein.
  • Bicarbonate Secretion: It releases bicarbonate, which helps neutralize stomach acid. This makes the food less acidic, allowing the digestive enzymes to work better.
• Endocrine Function (Hormone Production):
  • The islets of Langerhans produce important hormones:
    • Insulin: Lowers blood sugar levels.
    • Glucagon: Raises blood sugar levels.

pH of Pancreatic Secretions:

• The liquid produced by the pancreas (pancreatic juice) is slightly alkaline, with a pH of about 7.5 to 8.5. This means it is not too acidic. This is important because it helps to neutralize the acid from the stomach, making it easier for digestive enzymes to do their job.

Summary:

The pancreas in chickens plays a crucial role in helping them digest food and manage their energy levels. It makes digestive enzymes and neutralizes stomach acid to help with digestion and produces hormones to keep blood sugar levels balanced.

 

LIVER

 

Where is it?
The chicken liver is a brown, multi-lobed organ located beneath (ventrally) and behind (posteriorly) the heart. It is near the proventriculus (part of the stomach) and the spleen. When chickens are very young (10-14 days old), their livers can look pale because they are using nutrients from the yolk. In adult chickens, the liver weighs about 50 grams. A thin covering called Glisson’s capsule protects it. The liver also has a gall bladder on the right side that stores

Functions:

The chicken liver has several important jobs:

• Makes Bile: The liver produces bile, a liquid that helps digest fats. Bile is made of bile salts and pigments.
• Metabolism: The liver helps process nutrients from food:
  • Carbohydrates: They help control blood sugar by storing and converting glycogen (a type of sugar).
  • Lipids (Fats): It processes fats for energy and storage.
  • Proteins: It makes important proteins that help blood clotting and keep the body healthy.
• Blood Cell Production and Destruction: The liver helps produce and break down blood cells.
• Storage: It stores glycogen, fats, and vitamins (A, D, E, K) that the body needs.
• Detoxification: The liver cleans the blood by breaking down and getting rid of harmful substances.

Liver Facts

• Regenerative Ability: The liver can heal itself even after serious damage. This means if it gets hurt, it can grow back.
• pH Level: Chicken bile has a pH of 7.5 to 8.5, making it slightly alkaline (which means it’s not too acidic). This helps break down fats during digestion.

Summary

The chicken liver plays a vital role in producing bile, processing nutrients, detoxifying the blood, and storing energy. Its ability to heal is essential for keeping chickens healthy and strong!

 

SMALL INTESTINE :

 

In the digestive system, The small intestine of a chicken is a long, twisted tube that measures about 2 to 4 meters! It has three main parts:

Duodenum

• This is the first part of the small intestine. Here, digestive juices from the pancreas and bile from the liver mix with the food. This mixture is called chyme.

Jejunum

• This middle section does most of the work when it comes to absorbing nutrients from the food.

Ileum

• The last part of the small intestine, the ileum, finishes the absorption of nutrients and connects to the large intestine.

Special Features

• Inside the small intestine, there are tiny finger-like structures called villi. Each villus has even smaller hair-like structures called microvilli. These help to make the surface area much bigger, which helps the chicken absorb more nutrients from its food.

What Does the Small Intestine Do?

Digestion

• The small intestine breaks down food into smaller pieces so that the chicken can absorb them. Special chemicals called enzymes and bile help digest proteins, carbohydrates, and fats.

Absorption

• The walls of the small intestine take in important nutrients like amino acids (from proteins), fatty acids (from fats), vitamins, and minerals. These nutrients then enter the chicken’s bloodstream.

Immune Defense

• The small intestine helps protect the chicken from harmful germs that might come from the food it eats.

Fermentation

• At the junction where the small and large intestines meet, there are two pouches called ceca. These help to ferment fibrous materials, making it easier for the chicken to absorb more nutrients.

pH Levels

The pH (a measure of how acidic or basic something is) in different parts of the small intestine varies:

• Duodenum: The pH is between 6.0 and 7.5. This is because it mixes the acidic chyme with alkaline (basic) bile and pancreatic juices.
• Jejunum: The pH is about 7.0 to 7.5, which is neutral.
• Ileum: Like the jejunum, it has a neutral to slightly alkaline pH for the best absorption of nutrients.

Summary

In the digestive System of Chicken, The small intestine is very important for a chicken’s digestion and overall health. It helps break down food, absorb nutrients, and even protects the chicken from germs. Its long, folded structure with villi and microvilli makes it really good at absorbing what the chicken needs to grow strong and lay eggs.

There is a small pouch called Meckel’s diverticulum near where the small intestine meets the large intestine. This pouch doesn’t do much but is interesting to know about!

 

LARGE INTESTINE

 

What is the Large Intestine?

• The large intestine in chickens is a short tube about 4 inches long.
• It runs straight beneath the backbone and ends at a part called the cloaca.

What is the Cloaca?

• The cloaca is a special chamber where three systems meet:
  • Digestive (food waste)
  • Urinary (liquid waste)
  • Reproductive (egg-laying)

Parts of the Large Intestine:

• The large intestine consists of two main parts:
  • Colon: The main part that helps with processing waste.
  • Rectum: The end part where waste is stored before being removed from the body.

Special Feature: The Bursa of Fabricius

• Near the cloaca, young chickens have a small organ called the bursa of Fabricius.
• This organ is important for helping their immune system fight off germs and diseases.
• The bursa usually goes away when the chicken is about one year old.

Functions of the Large Intestine

The large intestine has three main jobs:

Water Absorption: It takes back water from leftover food that the chicken can’t digest.

Drying Food Waste: It dries out the indigestible food to prepare it for getting rid of.

Waste Elimination: It helps the chicken get rid of waste through the cloaca.

Nutrient Absorption

• Most nutrient absorption (taking in good stuff from food) happens in the small intestine.
• The large intestine is very important for reabsorbing water and managing waste.

pH Level

• The pH level in a chicken’s large intestine is usually between 6.0 and 7.0.
• This means it has a slightly acidic to neutral environment, which helps with digestion.

Summary

• The chicken’s large intestine is short and plays an important role in water absorption, drying waste, and eliminating it.
• It is much shorter than the small intestine and ends at the cloaca, where waste is removed from the body.

 

CAECA

 

What are the Caeca?
Chickens have two special pouches called the caeca (pronounced “see-ka”) in their digestive system. Each caecum is about 16-18 cm long, which is roughly the length of a large ruler!

Where is the Caeca Located?
The caeca are positioned at the end of the small intestine and are attached by a thin tissue called the mesentery.

Structure of the Caeca

Each caecum consists of different parts and layers that help with digestion:

• Parts of Each Caecum:
  • Narrow Base: The thick-walled beginning part that connects to the small intestine.
  • Middle Section: A thinner, more flexible part.
  • Wide Apex: The end of the caecum, which is wider and has thicker walls.
• Layers of the Caeca:
  • Serous Membrane: The protective outer layer.
  • Muscle Layers: Both outer and inner muscle layers help move food along.
  • Mucous Membrane: This layer aids in nutrient absorption and contains tiny nerves for digestion.

Add also: Chicken Reproductive Anatomy

Functions of the Caeca

The caeca performs several important functions:

Fermentation: They help break down tough plant materials. Chickens eat a lot of grains and plants, which can be difficult to digest. The caeca contain bacteria that ferment these fibrous foods, making nutrients easier to absorb.

Nutrient Absorption: After fermentation, the caeca assists in absorbing valuable nutrients, such as vitamins and minerals, from the digested food. This helps chickens get more energy from what they eat.

Water Reabsorption: The caeca also play a role in absorbing water from the digested food, helping to keep the chicken hydrated.

The caeca contribute to the immune system by producing antibodies that protect chickens from harmful bacteria.

pH of the Caeca

The pH level in the caeca is typically neutral to slightly alkaline, usually around 6.5 to 7.5. This pH range is crucial for the bacteria in the caeca to thrive and effectively break down plant materials.

Summary

In summary, the caeca in chickens are two important pouches that measure about 16-18 cm long. They aid in fermentation, nutrient absorption, water reabsorption, and immune support. Their pH is neutral to slightly alkaline, which is ideal for digestion.

 

The Secret to a Healthy Chicken: Understanding Their Digestive System

 

Chickens have a unique digestive system that allows them to process a variety of foods efficiently. Each organ, from the crop to the gizzard, plays a crucial role in breaking down nutrients. This efficient system enables chickens to thrive on a diverse diet, making them resilient and adaptable creatures.

Understanding the intricacies of a chicken’s digestive system is essential for ensuring their optimal health and well-being. A balanced diet can help your chickens live longer and healthier.