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B87 The Digestion Process. Introduction Types of Digestive Systems Ruminant Digestion The Digestive Process. Lesson Outline. Introduction.
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Introduction Types of Digestive Systems Ruminant Digestion The Digestive Process Lesson Outline
Introduction • The basic function of the digestive system is to convert the basic nutrients taken in by the animal to a form that the body can use and then transport the nutrients to the cells where they are needed.
Introduction • The organs that make up the digestive system are known as the gastrointestinal tract. • The digestive system includes all the structures involved in the procuring, chewing, swallowing, digestion, absorption and excretion of feed.
Types of Digestive Systems • There are basically two types of digestive systems. • Monogastric: Single stomached animals • Ruminant: Multicompartment stomach.
Monogastric Digestive System • Simple stomach animals are not capable of digesting large amounts of fiber and are usually fed concentrate feeds. • Monogastric animals include… • Pigs • Horses • Rabbits • Dogs • Cats • Birds
Horse & Rabbit Digestive System • The horse and rabbit have an enlargement know as a cecum that enables the animal to utilize high fiber feeds by means of microbial fermentation.
Ruminant Digestion • Cows, sheep, and many species of wildlife are ruminants. • Any animal that regurgitates it’s food and chews it’s cud is a ruminant. • The digestive system of a ruminant differs in many ways. • In the mouth of ruminants there are no upper front teeth. Instead there is a dental pad that works with the lower incisors for tearing off forages and other feed stuffs.
Ruminant Digestion • In the back of the mouth the upper and lower jaw have molars that enable the animal to chew on one side of the mouth at a time. • Large quantities of saliva are produced. This saliva is high in phosphorus, urea nitrogen and sodium which supplies nutrients to the microorganisms in the stomach. • Unlike monogastric animals there are no enzymes in the saliva.
Ruminant Digestion • The stomach of ruminants have four compartments: • The rumen • The reticulum • The omasum • The abomasum
Reticulum • As ruminants graze, they tend to pick up hard indigestible objects such as small stones, nails and bits of wire. • These heavy materials fall into the reticulum. • The reticulum makes up about 5% of the total stomach capacity. • The walls of the reticulum are made up of a network of sub compartments much like a honey comb. • These small compartments trap and provide a storage place for hardware that does not float.
Reticulum • This prevents dangerous objects from proceeding through the rest of the digestive tract. • The reticulum also functions to store, sort and move feed back into the esophagus for regurgitation or into the rumen for further digestion. • After the fluids pass through the reticulum, they move into the rumen.
Rumen • The rumen, which is 80% of the total stomach, functions as a giant storage vat where food is soaked, mixed, and fermented by bacteria. • It sits on the left side of the abdominal cavity it is lined with tiny papillae (tiny nipple like projection) that aid in the absorption of nutrients. • Bacteria thrive in the rumen environment and function to break down fiber and cellulose.
Rumen • Volatile fatty acids are released as carbohydrates are broken down into starches and sugars. • These fatty acids are absorbed through the rumen wall to provide energy. • Bacteria also use nitrogen to form amino acids or protein. The bacteria can also synthesize water soluble vitamins and vitamin K.
Rumen • Byproducts of the microbial activity include methane and carbon dioxide. • Most of the gas is eliminated by belching. • If the gases are not eliminated due to froth or foam blocking the esophagus, the animal will bloat. • Bloat can be fatal. Muscles in the diaphragm are unable to expand to allow the lungs to fill with air, and the animal suffocates.
Omasum • After leaving the rumen, feed travels to the omasum, witch is 8% of total stomach volume. • The omasum grinds roughage using blunt muscular papillae that extend from many folds of the omasum walls.
Abomasum • The abomasum is the true stomach of the cow. It makes up about 8% of the total stomach volume. • It contains glands that excrete acids and contain enzymes which break down feed in the same way the stomach in a monogastric animal works. • By the time the feed reaches the abomasum, fiber has been broken down to the extent that it can be digested by the abomasum.
Abomasum • By means of an esophageal groove, milk goes directly to the abomasum for digestion in young ruminants. • Young animals are not born with microorganisms in the rumen, and without microorganisms, little if any digestion will occur in the rumen. • It takes time and fiberous feed for microorganisms to grow.
Accessory Organs • The pancreas secretes enzymes to break down fat. • The liver (largest internal organ) secretes bile, which digests fats and stores iron.
The Digestive Process • The digestive process begins at the mouth. • The tongue is used to grasp food, mix it, and swallow. • The teeth are used to mechanically break down the feed into smaller more digestible pieces. • The mouth also contains salivary glands which excrete saliva.
Saliva • Saliva contains several substances: • Water to moisten the feed. • Mucin to lubricate the feed. • Bicarbonates to buffer acids in the feed. • In monogastric animals, it contains the enzyme amylase which starts breaking down carbohydrates.
The Digestive Process • The process of digestion involves both a physical and a chemical break down of feed. • The walls of the stomach secrete hydrochloric acid that dissolves food. • It secretes pepsin which breaks down proteins into amino acids. • It secretes Renin which curdles milk. • It secretes lipase which cause the breakdown of fats to fatty acids and glycerol.
Small Intestine • The small intestine is a long coiled tube connecting the stomach to the large intestine. • The rest of the digestion and absorption takes place here. • The surface is covered with villi which provide surface area and allow absorption into the blood stream.
Large Intestine • The last organ of the digestive track is the large intestine. • The first part of the large intestine consists of the cecum. • The cecum serves little function on most Monogastric animals except for the horse.
Large Intestine • The second part of the large intestine is the colon, which is the largest part of the organ. • Its function is to provide a storage place for wastes from the digestive process. • Water is removed here and further digestion occurs on fibrous materials. • The rectum is the final part of the digestive system. It serves to pass waste material through to the anus where it is eliminated.
