The Goat Digestive Tract
Understanding our goat's digestive system is vital to keeping our goats healthy. Knowing the unique process that goats use to digest their food can help us make better choices about what to feed our goats, what supplements to offer, and how to prevent bloating, scours, and nutritional deficiencies. Keep reading if you want to learn more about the goat digestive tract.
The 7 main parts of the goat digestive system
There are 6 main parts to the goat's digestive system:
- mouth
- esophagus
- 4-chambered stomach including the rumen, reticulum, omasum, abomasum
- small intestine
- cecum
- large intestine
- rectum
Each of these parts acts like a processing station, preparing the food for the next stop and drawing out nutrients as it moves along the line.
The mouth
Goats are natural grazers which means they are constantly eating as they go about their day. Basically, they chew all day. If they're not eating, they're chewing cud. They have lower incisors (front teeth), but they do not have upper teeth, instead, they have a dental pad that they grind their food against.
When we chew, our jaw moves up and down, when a goat chews its bottom jaw moves in a circular motion, smearing and smashing food against the dental plate. They also have molars in the back of the jaw on the bottom. These teeth grind and mash the food as well.
The first step in the digestion process comes in the form of saliva. As a goat chews it mixes its food with saliva creating a slippery mass that can move easily down (and up) the esophagus.
The esophagus
The goat esophagus is bi-directional, meaning food is able to move down and back up the esophagus through muscle contractions. This contraction also helps squeeze and break down the food further. When a goat is grazing it is swallowing food down its esophagus into the first chamber of the goat's stomach or the rumen. When it stops grazing it begins to ruminate or begin the second step of the digestion process.
Chewing the cud
Ruminating happens when the goat stops grazing, it lies down and chews its cud. The goat "regurgitates" the food and sends it back up the esophagus. The food (now called cud) is chewed into smaller, more "digestible" pieces and is mixed with saliva. The goat swallows again until the contents of the cud are small enough to move on to the next process in digestion. Enzymes in the saliva help to break down the fibrous food particles and also lubricate the food mass as it moves through the esophagus.
When a goat regurgitates its cud, it is not the same as a human when they vomit. The cud is not exposed to stomach acid the way our food is. The cud is very neutral in pH usually around 6.5 on the pH scale. Water is 7.
The 4-chamber stomach
The rumen
The rumen is the first and largest chamber of the 4 chamber stomach in a goat. It comprises 80-85% of the 4-part stomach chamber. Basically, it is a large storage and fermentation vat that uses beneficial bacteria to break down the food so that nutrients can be drawn out and food can be moved along to the next station in the digestion process.
The rumen is located on the left side of the goat and if your goat is laying down, or is heavily pregnant you may see a wave motion moving down the left side of your goat. This wave is a muscle contraction That churns the feed in the rumen.
The rumen layers
As you can see from the drawing, the rumen holds gasses at the top, then today's food is called a fiber raft in the middle. This fiber raft floats on top of the liquid layer in the rumen. This liquid is a mixture of saliva, enzymes, and healthy gut microbes. Yesterday's food is at the bottom, it is ready to pass on to the next phase of digestion.
A goat holds food in its rumen for 48 hours.
As the goat's rumen contracts, the cud mass dips into the biome liquid, inoculating the food with beneficial bacteria. These bacteria break down the cell walls of the vegetation and make nutrients available. The rumen is covered in tiny finger-like structures called papillae, these structures increase the surface area of the stomach so that nutrients absorb quickly.
In the rumen, more than half of the carbohydrates in the goat's food convert to energy. The rumen also helps draw proteins from the food. Goats also gain protein from the large numbers of dead bacteria that cycle through the rumen.
The reticulum
The reticulum, or the reticulo-rumen, is a lower chamber within the rumen. Food that is small enough, is let into the lower chamber through a muscle that separates the reticulum from the rumen. If the food is not small enough, the muscle sends the food back up the esophagus to be chewed again as cud.
The reticulum is often called the honeycomb because of the honeycomb structure. This structure works like a fine filter collecting the smaller pieces of food and rejecting the larger ones. The microbiome in the reticulum draws further nutrition in the digestion process.
The omasum
After the reticulum the food makes its way to the omasum. This is the smallest chamber in the 4-part stomach, it is made of flaps or folds of tissue. These folds extend the surface area so the most nutrition is drawn out of the food. Nutrition is absorbed into the omasum folds.
The goat diet consists of brush, dead leaves, twigs, and otherwise low-nutrient-dense food. The 4-chambered stomach ensures that every morsel of nutrition is drawn from the goat's sparse diet.
The abomasum
Now we move to the abomasum or the "true stomach" of the goat. It is called the "true stomach" because this chamber is more like a human stomach and contains stomach acid. Any food particles that are left over from the process of moving through the other 3 chambers are digested in this stomach with highly acidic gastric juices and enzymes.
pH 1.5-2 human stomach
pH 2.5-3 goat abomasum
Goat kids have the largest abomasum because they drink milk and need to digest the milk like other mammals. As the goat kids begin grazing, the rumen and other parts of the stomach begin to develop.
The small intestines
After the abomasum, the food moves into the small intestine. Major nutrients absorb into the small intestine and move into the blood system. The acidity of the small intestine is more neutral due to the enzymes that draw out the nutrients. Probiotics and the small intestine microbiome turn the last stage of food into manure.
The cecum
The cecum is a joining point from the small intestine to the large intestine. It is a mucus membrane that draws out salt and moisture from the manure.
The large intestine
As the manure moves into the large intestine almost all the water is drawn out and with it, the last bit of nutrients.
The rectum
Finally, we move into the last stop of the goat's digestive system. The rectum stores the manure pellets until it passes out of the animal as stool.
Why is goat poop shaped like oval pellets?
Did you ever wonder why healthy goat poop is shaped like oval-shaped pellets? Remember the balls of cud I talked about earlier? Those balls represent the shape and amount of food that gets passed through the digestion tract at a time. A goat does not digest a meal all at once, but instead breaks down small amounts at a time, and sends those through the chambers of the stomach. Each of those food amounts comes out as an individual pellet.
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