Technically speaking, chickens have two different parts to their stomach - but they only have one stomach. Chickens have a proventriculus stomach, which is where digestive enzymes are added, and a gizzard which is a muscular organ that grinds up the food.
Chickens - and this is true of all birds - have very different digestive systems from us. In this article, I’ll explain how many stomachs a chicken has, and how their digestive systems work:
Do Chickens Have a True Stomach?
Chickens do have a true stomach, yes - it’s called the proventriculus stomach. The proventriculus is a glandular stomach where digestion begins for birds.
In the proventriculus, digestive enzymes and hydrochloric acid are added to the food to start breaking it up and preparing the food for digestion.
This isn’t too dissimilar to us. Our stomachs are organs with strong muscular walls that hold food while it’s mixed with enzymes to break the food down.
The difference with chickens is that the proventriculus is a long, thin organ and it’s connected to a larger, rounder organ called the gizzard.
It’s in the gizzard that food is ground up or ‘chewed’. The gizzard does this using strong contractions, and combined with grit and bits of hard materials it’s able to further break up harder food.
How Many Stomach Compartments Do Chickens Have?
Chickens have two stomach compartments or chambers; the first is the proventriculus, which is the first part of the stomach food enters and is mixed with gastric juices.
The second compartment is the gizzard. This is where food is crushed, chewed, mechanically ground - whatever term you want to use for breaking the food down.
The reason why chickens have a gizzard is because they do not have teeth. Chickens are not able to chew food before swallowing it, so it enters their stomachs in large pieces.
The gizzard essentially does the job of teeth by chewing up food before the final digestive process takes place.
Nutrients are absorbed by the chicken, and the waste is passed as poop and pee (in the form of uric crystals).
How Does a Chicken’s Digestive System Work?
To explain how a chicken’s digestive system works in simple terms, food takes the following journey after it’s eaten by a chicken:
- Food enters the crop - After food is swallowed, it’s collected in an area called a ‘crop’. This is basically a storage area located in front of a chicken’s breast area. You can usually see the crop swelling throughout the day as a chicken eats more food. The crop typically empties overnight, and the food travels into the proventriculus stomach.
- Food moves into the proventriculus stomach - With the food in the first compartment of the stomach called the proventriculus, digestive enzymes are added to soften and start breaking up the food.
- Food moves into the gizzard - The gizzard is the second stomach ‘compartment’, and sometimes confused for being a second stomach. This is where food is ground up into smaller pieces. It does this by contracting and with the aid of grit chickens are able to break up some tough food material.
- Food moves into the small intestine - With food broken down into small pieces, it enters the small intestine. This is where nutrients are absorbed as it travels through small pouches called the ceca.
- Food moves into the large intestine - The large intestine or colon is where the last of the reabsorption takes place.
- Waste (poop) exits via the cloaca - Chickens have one ‘exit hole’ where feces, pee, and eggs come out. Any nutrients that are not absorbed are passed out as waste - and chickens poop a lot!
Related - How are chickens laying eggs?
How Long Does It Take Chickens to Digest Their Food?
If you own chickens, I'm sure you've observed them eating and pooping all day long.
It certainly feels like chickens poop almost as quickly as they can gobble food up, but food does have to travel a fair distance from beak to exit.
The amount of time it takes food to pass through the digestive tract of a hen varies based on a number of factors, but there have been some studies on the topic.
One study I was able to find that has been posted on usda.gov, dates back to 1878 but is still cited today.
A farmer simply fed some chickens the same diet of leaves for a number of days, then switched up the diet to grains.
He waited to see how long it was before the grains started to come out in the chicken’s poop and recorded seeing some grains after 3 hours and 25 minutes.
Personally, this is faster than I would expect and faster than I've seen a lot of other people saying they've seen food passing through their hens.
I think it really depends on the food, the hen, how much they’ve eaten recently, and some other factors.
We also know that sometimes a hen will store food in its crop and not empty it into its digestive system for up to 24 hours.
There you have it, the best way to explain how many stomachs chickens have is that they have one, with two compartments.
A chicken’s digestive system is cleverly designed with a workaround to not having teeth, I find it pretty interesting.
As I’m sure you’re well aware, chickens are able to gobble up just about everything and anything they come across with very few problems.
Image credits - Photo by Vito Natale on Unsplash
Rate of Passage of Food Through the Digestive Tract of the Hen - Usda.gov