Exam 4 (Lecture 49) - Hindgut Fermentation Flashcards
Name the two main structures of the equine hindgut.
1) Cecum
2) Colon
Fermentative digestive process in the _________ is not as efficient as in the ___________. However, the physiology is very similar.
Horse; ruminant
List the conditions required for optimal hindgut fermentation.
1) Substrate supply
2) Control of pH and osmolality
3) Numerous and diverse types of anaerobic microbes
4) Retention of fermenting material
5) Continual removal of residue and waste products
Name the substrate (CHO/cellulose, protein, or fat) required for hindgut fermentation.
CHO/cellulose
_____________ and related molecules pass through the small intestinal tract. Plant material may be softened and swollen prior to entry into the cecum.
Cellulose
A large quantity of __________ generated in the equine large colon is wasted because there is no opportunity for absorption of amino acids.
Microbial crude protein (MCP)
Hindgut fermentation is aided by the effects of soaking and acid exposure on plant particles in the ___________. Increases susceptibility to microbial action which _________ rate of digestion in the hindgut.
Stomach
Increases
How do the microbes acquire N for fermentation?
1) There is extensive N recycling into the colon and cecum (like in the rumen)
2) Urea plus protein escaping SI digestion supplies the N needs of the microbes
3) Horses DO NOT have an efficient means of recovering microbial protein synthesized in the hindgut
- so most is passed in feces
Mixing action (segmentation) of the _________ maintains the cecal contents in a homogenous state.
Cecum
Briefly describe the type of motility pattern located in the cecum (slide 5).
1) About once every 3-4 minutes there is a strong contraction of cecal muscles in a mass peristaltic movement type of action
2) Body and apex of the cecum shorten and constrict lifting ingesta into the base
3) Constriction of cecal base forces material through the ceco-colic oriface and into the RVC
4) Motility pattern functionally separates the cecum from the ventral colon
5) Horses DO NOT have retrograde flow of material from the colon back into the cecum
Briefly describe the two types of motility patterns located in the right and left ventral colon.
1) Haustral Segmentation:
- Mixing with no net forward movement
- Serves a mixing function that aids in promoting fermentation and bringing VFAs in contact with mucosa
for absorption
- Mixing occurs throughout the ventral colon
- RVC and LVC segments are regarded as one functional unit with homogeneous ingesta
2) Peristalsis:
- Propulsive
- Aboral peristalsis
- Ventral colon originates near the cecum and appears to occur as a continuation of the cecal mass
movements
Briefly describe the type of motility pattern located in the left ventral colon.
1) Retropulsive or anti peristaltic movements resist the flow of ingesta
2) Movement proceeds cranial (oral) or caudal (aboral) depending on pacemaker origin (ICCs)
3) Result in the retention and mixing of material in the ventral colon
4) Allows time for microbial digestion and preventing the washout of microbes
What is the function of the pelvic flexure?
Impedes movement of ingesta, causing it to be retained in the ventral colon
Squeezing action selectively retains relatively large particulate matter
- allows liquid and small particles to pass
As particle size __________, there is significant __________ of material in the colon and _________ passage to the feces. (Graph, slide 10).
Increases; retention; slow
The equine hindgut requires an efficient means of buffering and VFA absorption. Large quantities of fluid, rich in _________ and _________ buffers are secreted by the ileum and transferred to the cecum.
HCO3- and PO4-
