DIGESTIVE SYSTEM OF THE RABBIT: PARTS AND FUNCTIONS - BIOLOGY - 2025

The apparatus or system digestive rabbit, to equal that of many other vertebrates, consists of the digestive tract and by a digestive glands accessory associated to this. It is specialized for the rapid digestion of large amounts of food and is characterized by the relative importance of the colon and the cecum.

Rabbits are herbivorous animals with a high metabolic rate. They are folivorous, specifically, which means that they feed mainly on green leaves, usually rich in energy and fiber.

Rabbits eating carrots (Image by David Mark on pixabay.com)

Since they are domesticated animals, their body systems are "designed" to flee from their natural predators, for which they need to get the most out of the food they eat, which is why their digestion system has "evolved" or has " adapted ”considerably.

Since the food consumed by these animals is abundant in fibrous content, rabbits (as well as horses, guinea pigs and chinchillas) have developed a digestive strategy to process the dietary fiber they consume known as "hindgut fermentation. ”.

As is true of many other animals, the bacterial flora of the digestive system of rabbits, especially that associated with the cecum (the first portion of the large intestine that connects the small intestine with the colon), is of great importance to the process. digestive, that is, for the fermentation of the hindgut.

Parts

The digestive system of the rabbit, as already mentioned, is a complex system that includes the digestive tract and some glands associated with it and differs somewhat from the digestive systems of other animals.

The digestive tract consists of a tubular canal that runs through the body from the lips, through the mouth, to the anus.

The glands that are associated with this channel are located in the inner lining of the same, so they release the substances that they produce in the lumen (they are known as luminal glands). The main accessory glands of the digestive tract are the salivary glands, the liver, and the pancreas.

Photograph of a rabbit feeding (Image by Nancy Mure on pixabay.com)

In the digestive tract three well-defined regions are distinguished: the oral cavity or the mouth; the pharynx and the alimentary canal. The alimentary canal divides, in turn, into the esophagus, stomach, and small and large intestines.

The digestive tract

Since rabbits are herbivores, their digestive tract is quite long, which is intended to extract most of the nutrients from the green leaves they consume.

Your digestive tract is divided into:

- Oral cavity

- Pharynx

- esophagus

- stomach

- Small intestine

- Blind (oversized)

- Cecal appendix (or cecum)

- Colon

- Straight

- Year

Esophagus and stomach

It has been determined that adult rabbits can have food canals up to 5 meters long. They have a short esophagus, after which is a simple stomach (they are monogastric animals, unlike cows, for example, which have a stomach divided into four parts).

Up to 100 grams of what could be considered the "food bolus" are deposited in said stomach, a mixture of crushed and previously processed food mixed with saliva, which has a pasty consistency.

Anatomy of the intestine of a rabbit (Source: The original uploader was Sunshineconnelly at English Wikibooks. Via Wikimedia Commons)

Small intestine

"Connected" to the stomach is the small intestine which, in rabbits, is about 3 meters long and has a diameter of about 1 cm. The content of this portion of the digestive tract is mainly liquid.

Large intestine: colon, rectum and anus

Followed by the small intestine is the cecum, the first portion of the large intestine, prominent in these animals. The cecum also functions as a reservoir and is less than 50 cm long and 4 cm in diameter. Inside it houses more than 100 g of other pasta, characterized by containing almost 30% dry matter.

The cecum has what has been called a cecal appendix, which is a "limb" 10 to 12 cm long and of a smaller diameter, whose walls are made up of lymphatic tissue.

Close to the region of entry of the cecum, that is, of its union with the small intestine, is the first portion of the colon (the exit of the cecum). The colon of rabbits is about 1.5 meters long; Its first region is wavy and is called the proximal colon (50 cm), while its last portion is smooth and is known as the distal colon.

The terminal portion of the alimentary canal, which receives all the fecal material produced by digestion, is known as the rectum, which has an opening to the outside, the anus.

Accessory glands

Although the salivary glands play an important role in the early stages of food processing (for chewing and swallowing), the main accessory glands of the rabbit's digestive system, as well as that of other animals, are the liver and pancreas.

Both glands empty their secretions into the small intestine. The liver is responsible for the production of bile (rich in many different chemicals) and the pancreas produces pancreatic juice (which has abundant digestive enzymes for the breakdown of elements such as proteins, starches and fats).

Features

The digestive system of rabbits is responsible for the nutrition process, since it is involved in all the events through which the food passes from when it enters the mouth and is chewed, until its nutrients are absorbed and transported into the blood and lymph.

It differs considerably from the digestive system of other vertebrates and mammals in that the stomach and caecum contain almost 80% of the dry matter of the entire digestive tract.

When a rabbit is fed, the "pre-processed" matter that is swallowed quickly reaches the stomach, where the presence of an extremely acidic pH prevents the growth of almost any harmful microorganism. The "food bolus" remains there for a few hours, while some of the nutritive molecules contained in it are digested.

Photograph of a rabbit (Image by David Mark on pixabay.com)

Thanks to the abundant liver and pancreatic secretions, the stomach contents are diluted as it passes through the small intestine. Due to the action of the substances present in these glandular secretions, easily degradable molecules are released, and they are distributed throughout the body in the blood.

Those substances that are more fibrous and difficult to digest pass from the small intestine to the cecum, where they are processed by the bacteria present in the characteristic microflora of this compartment. What is left of this processing is emptied into the colon.

Two things can happen in the colon: that the rest of the undigested fibers are expelled as fecal matter (in the form of balls called "cecotrophies") or that the cecotrophies are "pushed" back into the cecum, a process during which they are " squeezed ”, extracting more nutritious fluids from these (this ends with the production of harder stool).

This last process is known as cecotrophy and it is one of the most resulting characteristics of the digestive system of rabbits.

References

1. Blas, C., & Wiseman, J. (Eds.). (2010). Nutrition of the Rabbit. CABI.
2. Davies, RR, & Davies, JAR (2003). Rabbit gastrointestinal physiology. Veterinary Clinics: Exotic Animal Practice, 6 (1), 139-153.
3. Kardong, KV (2002). Vertebrates: comparative anatomy, function, evolution (No. QL805 K35 2006). New York: McGraw-Hill.
4. Lebas, F., & FAO. (1986). The rabbit: breeding and pathology (No. 636.61 CON). FAO.
5. Richardson, VC (2008). Rabbits: health, husbandry and diseases. John Wiley & Sons.