By: Alisa Kowalski

Topic #3045 Digestion/Absorption

Ruminant

• An animal with 4 distinct compartments in its stomach, which swallows its food essentially unchewed, regurgitates it, chews it thoroughly and reswallows it.

• Examples: cattle, sheep, goats, deer, and elk

Nonruminants (Monogastrics)

• An animal having a single compartment in its stomach, which swallows its food after chewing and does not regurgitate it.

• Examples: pigs, humans, bears, and dogs

Ruminant Stomachs

• The four compartments are– Reticulum - honeycomb -5%

– Rumen - paunch -80%

– Omausm - manypiles -7%

– Abomasum - true stomach -8%

Reticulum

• Nickname - “hardware stomach”

• Furnishes additional storage space

• Holds foreign material to prevent damage to other internal organs– Examples: nails and wire

• A magnet may be fed to ruminants to catch and hold this foreign materials in the reticulum

Rumen

• Largest compartment– Capacity of 40-60 gallons in mature cattle

• Serves as a storage area

• Does not develop in young until solid food is ingested by the animal

Bacterial Action in Rumen I

• Reason why ruminants can digest large quantities and live on a much lower protein diet than monogastrics.

• As the bacteria multiply they make protein to construct their own bodies call bacterial protein.

Bacterial Action in Rumen II

• The bacterial protein is digested later in the stomach (abomasum) and the intestines of the ruminant

• Ruminants are able to consume a lower quantity and quality of dietary protein.

• The bacteria make up for it by multiplying and making protein from non-protein sources.

Omasum

• Muscular section that squeezes the water from the feed before it enter the abomasum

Abomasum

• “True stomach”

• Digestive juices containing enzymes cause chemicals changes to break down the proteins, carbohydrates, and fats into simpler substances which can pass into the small intestine for further digestion and absorption into the blood stream.

Regurgitation

• During the process of eating ruminants chew their feed just enough to make swallowing possible.

• After ruminants have consumed their feed, a bolus (food ball) is brought up form the rumen and chewing is completed.– Chewing their cud

Non-Ruminant Digestion

• Food is swallowed directly into the single compartment stomach, where it is mixed with the digestive juices.– Contains enzymes to break down foodstuffs

• Very little bacterial action

• No conversion of low quality protein to high quality protein

Non-Ruminant Digestion

• Monogastrics are unable to digest large quantities of fiber unless they have an enlarged cecum

• Animals with an enlarged cecum– Sometimes called pseudo ruminants– Examples: horses, rabbits, and guinea pigs

Non-Ruminant Digestion- Cecum

• Blind pouch at the first portion of the large intestine.

• Main place for bacterial breakdown in horses and rabbits

Digestion & Absorption by Livestock

• Digestion- the process by which large, complex food molecules are broken down into simpler molecules within the digestion system to prepare them for absorption and use by the body

Digestion & Absorption by Livestock - Enzymes

• Organic compounds which bring about changes in other organic compounds without themselves being changed or broken down.

• Break down complex feeds into simpler forms through chemical reactions

Importance of Chewing

• Chewing- physical process of breaking down foodstuffs to smaller particles.

• Increasing of surface area allow greater area for enzymatic activity

Digestion of Carbohydrates

• Must be broken down into simple starches and sugars before they can be absorbed in the small intestine.

• Begins in the mouth in animals whose saliva contains the enzyme ptyalin (non-ruminants).– Begins in rumen in animals without ptyalin

• The rest is digested and absorbed in the small intestine.

Bacterial Digestion of Carbohydrates

• Millions of bacteria and protozoa grow in the mass of water and feed in the rumen.– Secrete enzymes which digest the carbohydrates

and proteins– Reproduce and grow using the digested material,

primarily the protein

Bacterial Digestion of Carbohydrates

• During this process they also synthesize B vitamins

– Used in the nervous system & to release energy from digested nutrients in the host animal

• Because of this adult ruminants do not need dietary B vitamins

Bacterial Digestion of Carbohydrates

• Small amount of the digested cellulose and other carbohydrates is incorporated into the rumen “organisms”

• Most is converted into organic acids– Volatile Fatty Acids (VFAs)– Acetic, propionic and butyric– Absorbed directly through the rumen wall into

the capillaries of the circulatory system.

Bacterial Digestion of Carbohydrates

• Similar activities occur in the cecum of the horse and rabbit– Horses have little need for B vitamins due to this

• Relationship between the rumen protozoa & bacteria and the host (or ruminant) is called SYMBIOSIS.

• Way in which two organisms of two different species live in intimate association with each other

Relationships Between Organisms

• Mutualism - each helps the other– Example: man and dairy cow

• Commensalism - one benefits, the other does not– Example: Sheep tick on a sheep

• Parasitism - one depends on the other for some essential food factor, often detriment to host– Example: leech on fish

• Phoresis - the host transports the symbiont– Example: barnacle on a whale

Protein Digestion

• Broken down into peptides (smaller units) and amino acids (building blocks of proteins) in the stomach or abomasum of ruminants

• Begins in stomach with pepsin– Enzyme found in the gastric juices

• Final digestion in the small intestine where absorption also occurs

Fat Digestion

• Do not undergo digestion until they reach the small intestine

• Bile and enzymes from the pancreas help in the breakdown of fats so they can be absorbed in the small intestine.

Villi

• Line the intestines and are minute finger-like projections or papillae

• Provide a larger surface are in the lining of the intestine so there is more surface area for absorption of nutrients

Distribution of Nutrients

• Most nutrients are absorbed by the villi in the small intestine and enter the circulatory system

• The blood, containing these nutrients, reaches the capillaries in all the body tissues

• Here the nutrients pass through the capillary wall into the lymph (clear fluid occupying the space between the cells).

Distribution of Nutrients

• The nutrients then enter the cells, providing nourishment and energy for the various life processes