Ruminant Anatomy and Digestion

Introduction

• Ruminant animals' ability to use plant materials for production is linked to how well their gastrointestinal tract functions.
• Ruminant and non-ruminant animals handle food and digest it differently.
• The gastrointestinal tract begins at the mouth.
• Cheeks form the mouth's walls, the tongue is a soft organ, the hard palate sits above the tongue, and the pharynx is partially separated.
• Cattle's lips are stiff and not very flexible, while sheep and goats have more flexible lips, helping them pick feed faster.
• Understanding ruminant anatomy is essential for successful ruminant production.

Objectives

• Discuss the anatomy of the gastro-intestinal tract of ruminants.
• Identify the different segments of the gastro-intestinal tract of ruminants.
• Draw and label the gastro-intestinal tract of ruminant animals.

Digestion in the Mouth and Esophagus

• The digestive process begins in the mouth.
• Ruminants use a combination of their tongue and lips to grasp and manipulate plant material into the mouth.
• Teeth aid in the chewing of plant matter.
• Ruminants have two types of dentition.
• Young animals possess deciduous dentition, with dental formula I 0/4; C 0/0; P 3/3.
• Permanent dentition has the dental formula I 0/3; C 0/3; P 3/3; M 3/3, where I = Incisors, C = Canine, P = Premolar, M = Molar.
• Salivary glands in the mouth secrete saliva with a pH of approximately 8.2.
• Saliva buffers the mouth's pH, reducing acidity in the rumen.
• The esophagus is a tube that allows food to be swallowed and regurgitated for further chewing.
• The esophagus lacks sphincter valves, and its muscles contract in both directions for food movement.

Digestion in the Stomach

• The stomach makes up the largest part of the ruminant digestive system.
• The stomach has four chambers.
• The rumen is the first chamber, the reticulum is the second, the omasum is the third, and the abomasum is the fourth.

Digestion in the Rumen and Reticulum

• Digesta passes through the esophagus and enters the rumen.
• A thin wall divides the rumen and reticulum, and their contents mix.
• The rumen and reticulum are known as the reticulorumen because of the similarities between them.
• Fermentation of plant materials takes place in the rumen.
• Billions of microorganisms live in the rumen for this purpose.
• Young, unweaned animals have an esophageal groove, enabling milk to bypass the rumen and flow directly into the abomasum for digestion and absorption.

Digestion in the Omasum

• Digesta flows from the reticulorumen to the omasum.
• The omasum is a spherical organ with muscular laminae that absorbs water and inorganic minerals.
• The digesta is filtered to prevent foreign objects from entering the omasum.

Digestion in the Abomasum

• The abomasum is the true stomach and the first glandular part of the ruminant stomach where digestion takes place using enzymes.
• Gastric juice, containing hydrochloric acid, pepsin, and renin is produced in this chamber.
• In young, unweaned animals, the abomasum makes up about 80% of the stomach, while in adults, it only represents about 10%.
• The digesta remains in the abomasum for about 1-2 hours.

Digestion in the Small Intestine

• Further digestion of food digesta happens in the upper small intestine.
• Pancreatic juice and bile help with digestion, while the lower intestine uses villi to absorb the end products.

Digestion in the Large Intestine

• The large intestine consists of the colon and the cecum.
• Some food residue goes into the cecum for further fermentation; the cecum has a blind end containing microbes.
• The colon continues to absorb water and other nutrients.
• The digesta travels on to the rectum and anus.
• The undigested food material forms a solid mass in the colon and is expelled through the anus.

Conclusion

• The digestive system of ruminants features anatomical adaptations that enable functionality in each part of the gastrointestinal tract.

Summary

• The ruminant digestive system contains the mouth, esophagus, a four-compartment stomach (rumen, reticulum, omasum, abomasum), the small intestine, and the large intestine.
• Fermentation of plant material occurs in the rumen by billions of degrading microorganisms, which helps proper nutrient utilization.
• The abomasum is the true stomach where digestion occurs.
• The omasum, small intestine, colon, and large intestine are where water, inorganic minerals, and nitrogen are absorbed.