Ruminant Digestion

What are the 4 chambers of the ruminant stomach and which are forestomachs?

• Rumen (forestomach)

• Reticulum (forestomach)

• Omasum (forestomach)

• Abomasum (true stomach) #00a2ff

Forestomachs

• Function

• How

Function: Food is soaked, digested, fermented by microorganisms in the forestomachs before passing through the digestive tract

How:

• Bacteria and protozoa in the rumen and reticulum produce cellulase enzymes

• Which break down cellulose —> volatile fatty acids (acetic, propionic and butyric acids)

• Volatile FA are absorbed through rumen or intestinal wall —> blood

Where does most of the digestion occur?

Rumen

How can young ruminants be regarded as monogastric?

• Because their forestomachs are underdeveloped

• And their main food is milk which enters the abomasum directly through the oseophageal groove

Where does drier and more fibrous feed collect?

In dorsal sac and posterior region

Where does fluids, small particles and heavy materials collect?

In ventral sac, anterior region and reticulum

Rumination

• What

• Function

What: Ingesta from rumen is transferred back to the mouth where its' rechewed and reswallowed

Function:

• Leads to further reduction in food size

• Supplies new substrates for microbial digestion in rumen

Eructation #00a656

• What

• How can bloat occur

What: The release of gas from stomach or esophagus during microbial fermentation

How can bloat occur: If gases retained due to blockage of osophagus (could lead to death)

Rumen Microorganisms

• Bacteria

  • Cellulose digeting bacteria

  • Starch digesting bacteria

  • Soluble sugar digesting bacteria

  • Protein digesting bacteria

• Protozoa

  • Function

• Fungi

  • Function

Bacteria:

• Cellulose digeting bacteria: Acetic, lactic, butyric, small amounts of propionic acid

• Starch digesting bacteria: Propionic, lactic, small amounts of acetic and butyric acids

• Soluble sugar digesting bacteria: Acetic, lactic, butyric acids

• Protein digesting bacteria: Proteins and amino acids

Protozoa:

• Function: Utilize starch to produce acetic, propionic, butryic and lactic acids

Fungi:

• Function: Help break down plant wall

What is the constant environment of rumen microorganisms

• Body temp at 38-42C

• 5.5-7 pH

• Constant supply of food/water for microorganisms

• Slow turnover of food in rumen (24 hours)

• Maintenance of osmosis activities in rumen contents

Excess carbohydrate causes VFAs to build up which lowers the pH causes the microorganisms to die, what else will happen?

• No absorption and breakdown of cellulose

• No VFA absorption

• Causing accumulation of VFA

• Rumen acidosis

• Resulting to bloat

What are the 3 factors that influence balance of bacterial species?

• Geographical location

• Human intervention

• Genetic make-up of ruminant

What is the major end product of ruminant digestion?

Volatile fatty acids

What are the 3 major VFAs produced in rumen?

• Acetic acid #ff00c2

• Propionic acid #ff7f00

• Butyric acid #00b1ff

VFA: Acetic Acid #ff00c2

• What type of feed increases acetic acid production

• Function

What type of feed leads to more acetic acid production: Grass (high in cellulose)

Function: Lipid metabolism and milk fat synthesis in dairy animals

VFA: Propionic Acid #ff7f00

• What type of feed increases propionic acid production

• Function

What type of feed increases propionic acid production: Grain (high in starch)

Function: Carbohydrate metabolism for energy and growth in meat animals

Protein Metabolism

• What happens to dietary protein in rumen

• What happens to ammonia in rumen

• What happens to absorbed ammonia in liver

• Role of mircobial urase in rumen

• What is non-protein nitrogen used for in ruminants

What happens to dietary protein in rumen: Broken down into amino acids —> ammonia by microbial action

What happens to ammonia in rumen: Absorbed into bloodstream

What happens to absorbed ammonia in liver: Converted into urea

Role of mircobial urase in rumen: Converts urea —> ammonia for microbial protein synthesis

What is non-protein nitrogen used for in ruminants: Microbial synthesis of protein

Lipid Metabolism #ffbb00

• What is microbial biohydrogenation

Microbial biohydrogenation: Conversion of unsaturated FA —> saturated FA by microbes

Do ruminants have salivary amylase?

No

What ions are found in high conc of ruminant saliva?

Bicarbonate ions and urea

What is the main mechanism of digestion in ruminants

Relies on microbial activity from bacteria, protozoa and fungi

What do rumen microbes secrete to digest cellulose

Secrete cellulase (cellulose —> VFAs)

What gases are produced during rumen fermentation?

CO2, NH3, CH4, H2S, SO2

How are fermentation gases removed from rumen

Through eructation which is expelled by nasal passages

What happens to undigested fiber in ruminants?

Further digested by microbes in cecum