Rumen Fermentation and Function Flashcards
Consortia
Groups of microbes with a common net feeding strategy
Rumen liquor
Rumen liquid
What are the 4 compartments of the rumen
Rumen, reticulum, omasum and abomasum
The rumen functions as…
A fermentation vat
What is the capacity of an adult dairy cows rumen
184L
What is the function of papillae
Absorption of VFAs
What are the 5 sacs of the rumen
Cranial, dorsal, ventral, caudo-dorsal and caudo-ventral
Ruminal pillars divide…
The dorsal and ventral ruminal sacs
The coronary pillars divide…
The caudal blind sacs
Cranial pillar divides…
The dorsal and cranial sacs
Where does the most absorption occur in the rumen
The ventral part of the cranial and ventral sacs (where papillae is most dense)
What is a distinguishing feature of the reticulum
The honey combed shaped internal projections (trap foreign materials)
What separates the rumen from the reticulum (only partially)
Reticulo-ruminal fold
Where does the esophagus terminate
The cardia
What is the function of the reticulum
Moves food into the rumen or omasum and aids in regurgitation of ingesta during rumination
Where does the reticulum connect with the omasum
Reticulo-omasal orifice
What is the function of the omasum
Retention of feed in the rumen, absorb water and reduce size of food, control passage of food and some absorption
What is a property of the inside of the omasum
Has membranous folds that act as a sieve/filter (referred to as manyplies)
What is another name for the absomasum
True stomach
What is the normal pH of the rumen
5.5-7.5
What are some things that help stabilize the pH in the rumen
Phosphate and bicarbonate in the saliva
Rapid absorption of VFAs
Drinking water and saliva help dilute the rumen liquor
What type of diet promotes a higher rumen pH
High-forage diets
What diet decreases rumen pH
High grain diets
What is the osmolality of the rumen
Slightly under that of the blood
How is an anaerobic environment maintained in the rumen
Facultative anaerobic bacteria
What are 3 ways fermentation end products are continuously removed from the rumen
Passage of digesta to omasum
Absorption through the rumen wall
Eructation of CH4 and CO2
What are the general two phases of contents in the rumen
Lower liquid phase (finer food particles) and dried upper layer (coarser solid material)
What are three phases that materials entering the rumen can be in
Gas phase, floating rumen mat, liquid phase
Heavy feed falls into…
The reticulum
Light feed falls into…
The rumen proper
The floating or rumen mat contains…
Recently consumed feed, fibrous material
may be absent in diets high in concentrate
The liquid phase contains…
Smaller, dense particles (constant volume)
What are 3 types of contractions that occur in the cows rumen and reticulum
Mixing, eructation, and regurgitation
How are contractions of the rumen stimulated
Response to vagal sensory afferent information and initiation by vagus efferent nerves
What is the purpose of eructation contractions
Expel gas from the rumen, the contractions allow it so that gas can enter the esophagus and then the trachea and lungs, so that it is expelled in the next exhale
What help initiates the regurgitation reflex
The presence of a rumen mat (because its usually larger material that needs to be rechewed)
What are 3 populations in which rumen bacteria are found
Loosely/firmly attached to feed particles (majority)
In the rumen liquor
Attached to rumen epithelium (about 1%)
Cellulolytic bacteria
Produce extracellular cellulase, abundant in hay diets
Hemicellulolytic bacteria
Use hemicellulose
Amylolytic bacteria
Predominate with grain diets, significant proteolytic activity
Proteolytic bacteria
Utilize amino acids as primary energy source
Sugar utilizing bacteria
Use mono and disaccharides
Acid utilizing bacteria
Use Lactic/succinic acids to form propionate, mainly in high grain diets
Methane producing bacteria
Also known as archea
Cellulolytic bacteria: growth requirements and fermentation end products
Require: cellulose, hemicellulose, pectin - need a high rumen pH
Product: acetate, butyrate, H2, CO2
Amylolytic bacteria: growth requirements and fermentation products
Require: sugar, starch, peptides, AA - need a lower pH (5.7)
Products: Propionate, butyrate, acetate, lactate, H2, CO2
What are the two families of protozoa in adult ruminants
Holotrichs and oligotrichs
Holotrichs
Ovid organisms covered with cilia, store sugars until they burst
Oligotrichs
Include many species that vary considerably in size, shape and appearance
store starch
What is the interaction between protozoa and methanogens in the rumen
Rumen methane bacteria attach and live on the surface of rumen protozoa for access to hydrogen
Protozoa do not…
Easily pass from the rumen
Fermentation end products of holotrichs
Acetic acid, butyric acid, lactic acid and H2
Fermentation end products of oligotrichs
CO2, H2, acetic acid and butyric acid
Protozoa ingest…
Rumen bacteria as a source of protein (contributes to rumen protein turnover)
What are two phases of the fungi in the rumen
Motile phase (zoospore) and vegetative phase (sporangium)
Under normal conditions, the rumen fungi colonize…
Highly lignified fibrous material
What is the primary protein supply for ruminans
Microbial protein
How much of the animals energy needs are provided by VFAs
greater than 70%
Mature fibrous forages give rise to VFA mixtures with a high proportion of…
Acetic acid
Less mature forages give rise to VFA mixtures containing a high proportion of…
Propionic acid
VFAs are absorbed across…
The forestomach walls
VFA absorption is higher when…
Ruminal pH is reduced (more things present as undissociated acids)
Chain length increases
What is the venous drainage of the rumen
The hepatic portal vein, which goes into the liver
Lactic acid is produced during…
The degradation of starch
Unmetabolized lactic acid will cause…
Metabolic acidosis
How are the rumen gases removed
Eructation and respiration
Carbon dioxide accounts for how much of the gases produced by microbes?
60%
The fermentation of forages creates __ heat than the fermentation of concentrate feeds
More
Lactic acid is produced by…
Amylolytic bacteria
How does decreased rumen pH cause ruminal acidosis
Cellulolytic bacteria die, which release endotoxins that enter the blood and can cause shock
The increase in acid can also damage the rumen epithelium
What can cause ruminal acidosis
A sudden switch to a high grain diet (instead of slowly over time)
