How Many Stomachs does a Cow have

The stomach of a cow is a significant dilatation of the alimentary canal just behind the diaphragm. You will find a structural variation on a cow’s stomach compared to that of a dog or a horse. The animal lover has a common inquiry: how many stomachs does a cow have. Nice, today I will provide the complete answer to this question – how many stomachs does a cow have

Here, I will describe the different parts of the stomach of a cow with a labeled diagram. I will also tell you why cows have different parts in their stomach. You will also get more information about the stomach of other different animals like horses, sheep, goats, dogs, and so on in this article. 

Are you interested to know the number and different parts of cow’s stomach? That fine, let’s continue to the article till the end and learn the exciting facts about the stomach of a cow. 

How many stomachs does a cow have

First, I should tell you how many stomachs does a cow have. The cow has only one stomach, but it possesses four different compartments. A cow’s stomach is like a muscular bag forming the widest and expansive part of the digestive tract. This intervenes between the esophagus and the small intestine of a cow. 

Let’s see the four different parts of the stomach of a cow from the labeled diagram –

  • First compartment – rumen 
  • Second compartment – reticulum
  • Third compartment – omasum and 
  • Fourth compartment – abomasum.

The first three parts of the stomach are called the forestomach. Another name of forestomach is proventriculus, or esophageal sacculation. It possesses the non-glandular mucosa membrane in the inner aspect. No secretion will produce in the non-glandular part of a cow’s stomach. 

On the other hand, the fourth part of the cow stomach (abomasum) is the true stomach. It has a glandular mucosa membrane, so only this compartment is responsible for gastric secretion. 

The cow’s stomach fills up the most whole of the left half and a part of the right half of the abdominal cavity. On the left side, a small amount is left by the stomach to accommodate the spleen and a portion of the intestine.

How many stomachs does a cow have
How many stomachs does a cow have

The average capacity of the cow stomach is about one hundred to two hundred and thirty liters. Rumen occupies eighty percent of the total volume, reticulum five percent, omasum seven percent, and abomasum eight percent. The relative capacity varies in newborns and infants because they do not consume grass and other usual food. 

Size of cow stomach 

The relative size of the four compartments of cow stomach varies significantly with age. In a newborn calf, the rumen and reticulum together have about half the capacity of the abomasum. The abomasum is the largest of all the compartments in the calf because they live on milk. At eight weeks of age, the combined capacity of the rumen and reticulum equals that of the abomasum. 

Again, at the twelve weeks, the rumen and reticulum of a calf together has twice the capacity of the abomasum. The abomasum of newborn cows grows very slowly during this period. At one and half years, the omasum approximately equals the abomasum incapacity. Gradually, the four parts of the stomach reach their relative capacities, as I mentioned earlier. 

“In sheep and goat, the capacity of the stomach is about fifteen to eighteen liters. The rumen and omasum are relatively smaller than that of a cow. The rumen constitutes about seventy-one percent, the reticulum is about eight percent, the omasum two percent, and the abomasum is about nineteen percent.”

How many stomachs does a cow have, and why

So, you already got your answer for the question – how many stomachs does a cow have. If you want to know why there are four different parts in a cow stomach, you may simply continue this part of the article. Here, I will tell you the functions of four other parts of the stomach of a cow. I think you will understand why there are four different compartments. 

But before going to describe the functions of the four compartments of a stomach, you might know a little about a cow. Mainly, a cow is a ruminant animal, and they perform rumination. They use most of the time of the day for ruminating the feed. 

If you don’t know about the term rumination, this little information is for you. Rumination is the process of regurgitating previously consumed feed (soft feed wads) from the rumen and re-chewing it further. 

But why this rumination occurs in a cow? First, the cow takes grass, hay, or grain that mixes with saliva and store it in the rumen. They used to regurgitate and break it into small pieces. These small pieces of feed again re-salivate and re-swallow into the rumen of the cow stomach. Rumen microbes could easily digest the small fragments of feed particles. However, the rumen itself helps to break down the feed particles. 

The time of rumination may vary in older cattle and calf. Generally, older cattle spend little time ruminating compare to a calf. Again, the rumination may change with the diet you supply to your cow. If you provide grass or hay, the ruminating time might be more. And if your cow takes grain, the ruminating time will be less. 

Why rumen in a cow stomach

You know the first compartment of cow stomach is rumen and feed particle first comes into this part. The rumen contract moves continuously and performs some definite functions. 

An essential function of the rumen is to break down the feed particle into small pieces. It also helps to mix the ruminal contents. The rumen introduce the microbes to the mixed contents or small fragments of feed particles. It also helps to reduce the flotation of solids. 

In the rumen, the ruminal microbes convert the complex and straightforward fibers into energy. Again, the rumen microbes help produce vitamins that are essential for the growth and maintenance of a cow.

“These are the little information about the function of a rumen is cow stomach. You might also learn more about rumen and their whole process in feed digestion.”

Contributions of other parts of cow stomach

The other three compartments of a cow’s stomach also possess some unique functions. You know the second compartment of the cow stomach is the reticulum. The cow stomach reticulum will help collect the smallest digested particles and move them into the third compartment (omasum). 

“The larger particle of feeds will remain into the rumen for further rumination.”

Sometimes your cow may consume the nail, wire, or other foreign objects that will not digest. The reticulum of the cow’s stomach will trap and collect these objects.

You will find a large, well-developed omasum in the cow stomach. It is spherical and connects with the reticulum compartment with a short tunnel. Several folds (leaves like – I will show you later in this article) present in the inner aspect of an omasum. These folds of an omasum will increase the surface area and help absorb the nutrient from the feed and water. 

Again, the fourth compartment of a cow’s stomach is the abomasum, known as the true stomach. This compartment is similar to that of a non-ruminant stomach (like a dog, horse). The abomasum will produce a digestive enzyme that can digest protein and starch. It will also help to break down any undegradable feed particles that did not digest in the rumen. 

Anatomy of a cow stomach (how many stomachs does a cow have)

You probably have your answer to this question – how many stomachs does a cow have and why. Now, I will discuss the external and internal anatomy of a cow stomach. If you are interested to know these anatomical features of a cow stomach, you may continue this article again. 

Though I have a detailed guide on ruminant stomach (I have taken an example from a goat) here in anatomy learner. So, I will not go into the details anatomy of cow stomach. Instead, I prefer to provide unique anatomical features from the different compartments of a cow stomach. 

Surface anatomy of cow stomachs

If you are a veterinary student, you might know the surface anatomy of a cow stomach. But, if you are a cow lover or farm owner, you may see this surface anatomy to fine-tune your knowledge. 

  • Surface anatomy of rumen 
  • Surface anatomy of reticulum
  • The omasum and its surface anatomy
  • Surface anatomy of the abomasum 

Let’s start with the surface anatomy of the first compartment of the cow stomach. 

Surface anatomy of rumen

The first compartment of the cow stomach (rumen) occupies most of the left half of the abdominal cavity. It extends considerably to the right of the median plane ventrally and caudally. The long axis of the cow’s rumen extends from the ventral part of the seventh or eighth intercostal area to the pelvic inlet (transverse plane of tuber coxae).

The contraction of a rumen may be palpated in the paralumbar fossa. If you don’t know what a paralumbar fossa is, then I will tell you a little about this structure. The paralumbar fossa is a triangular depressed area at the left flank region of a cow. 

If you try to palpate at the paralumbar fossa, you will find the dorsal sac of rumen. Again, the ventral sac of rumen lies on the ventral abdominal wall caudal to the transverse plane of the ninth intercostal junction. 

Surface anatomy of reticulum

The reticulum is the most cranial and smallest of the four compartments of a cow stomach. It is somewhat piriform in shape and compressed craniocaudally. The more significant part of the reticulum lies on the left half of the median plane of the body. 

It contacts the left abdominal wall at the ventral ends of the sixth and seventh intercostal space. The reticulum is also in contact with the ventral wall of the abdomen in the corresponding sternal region.   

Surface anatomy of the omasum 

The omasum of a cow stomach is ellipsoidal and somewhat compressed between its parietal and visceral surfaces. It is marked off from the other compartments of the cow stomach. The long axis of the omasum compartment is nearly verticle. 

It lies to the right of the median plane, opposite to the seventh to eleventh ribs. The parietal surface faces obliquely to the right that relates mainly to the diaphragm and liver. Again, the ventral part of the omasum is in contact with the abdominal floor.

“In short, the omasum compartment of cow stomach is in contact with the right abdominal wall in the ventral part of seventh to tenth intercostal spaces. It also contacts the abdominal floor in a small area between xiphoid cartilage and the right costal cartilage.”

Surface anatomy of the abomasum

The fourth and also most important compartment of the cow stomach is the abomasum. You may need to collect abomasal fluid for diagnostic purposes (if you are a veterinarian). So, you might know the proper location of the abomasum of a cow’s stomach. 

The abomasum of the cow stomach is an elongated sac-like structure that lies on the abdominal floor. If you read my previous article on goat stomach anatomy, you will find three different parts in the abomasum. These three parts of the abomasum are – funds, body, and pyloric. 

The funds part of the abomasum is a blind end and lies on the xiphoid cartilage. Again, the body of the abomasum extends caudally between the ventral sac of rumen and omasum. It lies more on the left than on the right of the median plane of the body. 

In addition, the pyloric part of the abomasum runs to the right caudal to the omasum, is inclined dorsally, and joins with the duodenum. This part remains in between the ventral aspect of the ninth to eleventh intercostal spaces. The parietal surface of the abomasum is mainly in contact with the abdominal floor. 

So, how do you palpate and collect abomasal fluid from the abomasum compartment? Behind the xiphoid cartilage to the abdominal floor (left of the median plane) will be the best area for palpation and collecting abomasal fluid from the abomasum compartment. 

“If you are not a veterinarian, please don’t practice this method.”

External and internal anatomy of cow stomachs

Here, I will show you only the most important external and internal anatomical features of different compartments of a cow stomach. These anatomical features are somewhat different from that those of a horse’s stomach. This part of the article also helps you understand how many stomachs a cow have. 

Cow rumen anatomy with diagram 

The rumen is the large compartment of a cow’s stomach that possesses two surfaces, two curvatures, and two extremities. You will find the below-mentioned anatomical features from both the external and internal parts of cow rumen. 

  • Surfaces (parietal and visceral) of rumen
  • The curvatures (dorsal and ventral) of rumen
  • Two extremities (cranial and caudal) of rumen
  • The right and left longitudinal grooves of rumen 
  • Sacs of rumen (dorsal and ventral sacs)
  • The caudodorsal and caudoventral blind sacs of rumen at the caudal extremity
  • A deep, transverse caudal transverse groove at the caudal extremity
  • The ruminoreticular groove of rumen 
  • The dorsal and ventral coronary grooves of rumen
  • The pillar in the internal part of the rumen

I have shown you all the anatomical features in the previous cow stomach labeled diagram. Again, I will show you the internal anatomical features of the rumen. 

The parietal surface of the rumen is convex and related to the diaphragm. At the same time, the visceral surface is somewhat irregular and connected to the omasum and abomasum. The ventral curvature lies on the floor of the abdominal cavity. 

You will find right and left longitudinal grooves that will divide rumen into two sacs – dorsal and ventral sacs. There is a transverse cranial groove present in the cranial extremity of the rumen. In addition, you will find a deep caudal transverse groove at the caudal extremity of rumen that forms the caudodorsal and caudoventral blind sacs. 

Cow reticulum anatomy with labeled diagram 

The reticulum is the most cranial part of the cow stomach and posses two surfaces, two curvatures. The diaphragmatic surface of the rumen is convex and lies against the diaphragm and liver of the cow. In addition, the visceral surface flattened more or less by the pressure of atrium ruminis. 

The lesser curvature of reticulum faces to the right and connects with the omasum compartment. Again, the greater curvature faces to the left and lies against the diaphragm of the cow opposite to the sixth and seventh ribs. You will find around the structure (culdesac) in the reticulum that connects with the sternal part of the diaphragm, liver, omasum, and abomasum. 

Internally in the reticulum, you will find folds that present honey-comb like cells. These cells possess serrated edges (shown in the labeled diagram; get more here). 

Omasum and abomasum compartment of cow stomach

The parietal surface of the omasum compartment of the cow stomach lies against the lateral wall at the ventral part of the seventh to ninth intercostal spaces. You will find a connection with the rumen, reticulum, and abomasum at it’s a visceral surface (left). 

The dorsal curvature of the omasum faces dorsally, caudally, and to the right. Interiorly, the omasum fills with parallel muscular laminae (laminae omasi). These laminae of omasum look like the pages of a book, so omasum is also called the book of cow stomach. 

The abomasum is the fourth compartment that is a true glandular stomach of a cow. It presents three main parts – fundus, body, and pyloric. The funds are the cranial blind part of the actual stomach of a cow. In contrast, the body is the central part of the abomasum compartment. 

Internally, you will find three glandular regions in the abomasum compartment of a cow stomach. The fundus gland region of the abomasum presents numerous spiral folds. Again, the pyloric gland region of the stomach is much narrower and smaller. In addition, the cardiac gland region of the abomasum is a small confined area adjacent to the omasabomasal orifice. 

How many stomachs does a horse have to compare to a cow

You may also know – how many stomachs does a horse have compared to a cow. The horse also have one stomach but is different from that of a cow. You will find two parts (glandular and no-glandular) in the horse’s stomach. These two parts of the horse stomach are separate by a rough line (margoplicatus)

I have a detailed guide on horse stomach here on anatomy learner. If you want to learn the details anatomy of a horse stomach, you may read that article. I hope you will learn all the anatomical facts from horse anatomy. You will make a difference between the horse and cow stomach after completing that article. 

In goat and sheep, you will also find four different compartments as like a cow stomach. 

Frequently asked questions on cow stomach.

Here, I will try to answer all the questions on cow stomach anatomy that animal lovers or a future veterinarian asks. 

Why does a cow have 4 stomachs?

The cow or other ruminants like sheep or goat lives on grass, hay, or grain. These feed particles are break down within the first compartment (rumen) of the cow stomach. The cow stomach’s second compartment (reticulum) helps collect the digested feed particle and move them into the next chamber. 

Again, the third compartment of the cow stomach (omasum) increases the surface area that helps absorb nutrients from the feed particles. In addition, the fourth compartment (abomasum) has a similar function to the glandular stomach. 

Does a cow have 1 or 4 stomachs?

The cow or sheep, or goat has only one stomach. But the stomach of these ruminant animals possesses four different distinguished compartments – rumen, reticulum, omasum, and abomasum. 

Conclusion

I hope you got your complete answers to your question – how many stomachs does a cow have. All the ruminants like cows, sheep, goats possess only one stomach with four different compartments. But animals like dogs and horses will find one stomach with two distinct parts – glandular and non-glandular. If you are a veterinary student, I suggest you read my previous article on ruminant stomach anatomy. This article might help you learn the anatomical facts of four different compartments of a cow’s stomach.

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