Exam 2: Lecture 17: Non-ruminant Herbivore Digestive Physiology Flashcards
What are the 2 types of fermenters?
-Pre-gastric fermenters
-Hindgut fermenters
What is a pre-gastric fermenters?
-Fermenting material prior to the gastric stomach & small intestine
What animals are pre-gastric fermenters?
-Ruminants (sheep, cattle, goats, deer, camels)
-Non-ruminant herbivores that are foregut fermenters
What is a hindgut fermenter?
-Fermenting after the small intestine (so they have lost a large area of absorption)
What type of fermenters fall under hindgut fermenters?
-Cecal fermenters
-Colon fermenters (very large cecum & colon)
What animals are cecal fermenters?
-Rabbits
-Guinea pigs
-Chinchillas
-Rats
What animals are colon fermenters?
-Horses
-Gorillas
-Elephants
-Rhinoceroses
-Koalas
What has a huge effect on efficiency and utilization of fermentation products?
-Whether the animal ferments BEFORE or AFTER the gastric stomach and SI
Microbial fermentation in herbivores is only useful IF the digestive system can
-Retain digesta & microbes for long periods of time
-Maintain an environment suitable for fermentation (specific pH conditions, etc.)
What are the 3 factors for utilizing microbial fermentation?
-Volume available for fermentation (greatest in ruminants)
-Retention time
-Microbial populations similar in most species
Ruminants have over ____ of their GIT devoted just to fermentation
75%
Non-ruminant herbivores have _____ to facilitate microbial fermentation?
-GIT modifications
What are the GIT modifications in non-ruminant herbivores to facilitate microbial fermentation?
-Pre-gastric: have compartments within the stomach that will selectively sort & maintain the more fibrous material so you can ferment
-Hindgut: either a larger cecum and/or larger colon
What are the three groups of non-ruminant herbivores?
-Foregut fermenters
-Cecal fermenters
-Colon fermenters
Which species has an enlarged cecum and is considered a cecal fermenter?
A. Deer
B. Guinea Pig
C. Koala
D. Gorilla
B. Guinea Pig
Foregut fermenters have a _____ stomach
Compartmentalized
What is a compartmentalized stomach?
-One or more pouches for fermentation separate from gastric region
-Between 2-4 paths for fermentation
-Typically, we have an expanded cardiac region for fermentation
Foregut fermenters can be _____ feeders or _____
bulk roughage feeders or browsers
What animals are foregut fermenters?
-Soth (browser)
-Colobus monkey (browser)
-Kangaroos & wallabies (browse & graze)
None of the non-ruminant herbivore domesticated species are ______
Foregut fermenters
How many stomach chambers does the sloth have?
-Has a 3 chambered stomach
-Leaves they eat can take up to a month to digest
How many chambers does a kangaroo stomach have?
Not chambered as much as a long tube stomach w/ 3 main structures:
-Sacciform
-Tubiform (fiber digestion)
-Gastric
How many chambers does a colobus monkey stomach have?
-Most species within this monkey have 4 pouches or chambers
Who are cecal fermenters?
-Rodents
-Lagomorphs
Because the cecum is a blind sac in cecal fermenters, what has to happen to digesta?
-Digesta must pass out via route of entry (go in & out the same route)
-Allows cecum to selectively retain certain fractions of feed
Cecal contents enter colon _____ times/day
1-2 times/day
Cecal fermenters is an evolved strategy to
separate and excrete indigestible fiber
In cecal fermenters, the separation of particles is based on
the density of the colon
What happens to less dense material in the colon?
-Larger fiber particles remain in the lumen area (right in the center of the lumen) & they move on through the colon (they just keep on moving)
What happens to the denser, smaller particles in the colon?
-Remain around the perimeter (includes proteins, easily digestible fibers) & will move into cecum for fermentation
Cecal fermenters produce what feces?
-Hard feces
-Soft feces
What is in the hard feces of cecal fermenters?
-Will have your indigestible fibers
What is in the soft feces of the colon?
-Cecal contents that are coded w/ mucus -> then get consumed by animals -> lots of B vitamins from the microbes & there will be microbial protein from dead microbes that were in the cecum (which is great for providing AAs)
What is soft feces of the colon also called?
-Night feces
Hindgut/colon fermentation is limited in
Omnivores and some herbivores (ruminants)
What are the major hindgut functions?
-Primary site of microbial fermentation in colon fermenters
-Mixing of contents
-Ilium & colonic epithelial secrete bicarbonate
-Reabsorption of fluid & electrolytes
Why is the mixing of contents a major hindgut function?
-Movement within the hindgut to promote fermentation (so need mixing) & you need to expose contents to the mucosal surface b/c can then absorb products
-(Major products = VFAs)
What are the main 3 VFAs to remember that are products of fermentation & used for energy?
-Acetate
-Propionate
-Butyrate
Colon fermenters are ____ and have _____ for microbial fermentation
-Equids, elephants, koalas
-Enlarged colon & cecum for microbial fermentation
What is fermented in the enlarged colon and cecum for microbial fermentation in the colon fermenters?
-Ferments material that resists breakdown in SI AND starch/sugar that escapes SI digestion
Is hindgut fermentation more or less efficient and why?
-Less efficient (compared to ruminant or foregut)
-B/c you have less opportunity to absorb VFAs
-can’t utilize microbial protein here
Which type of feces in cecal fermenters is coated with mucus?
-Night feces (soft feces)
Substrates in the hindgut include
-Structural and non-structural carbohydrates, proteins
What are the structural carbs in the hindgut?
-Comprised of cellulose & hemicellulose (& lignin)
-Very hard to digest
-Acid exposure from gastric stomach can help increase susceptibility to microbes
What are the non-structural carbs in the hindgut?
-How much reaches the hindgut affects the animals risk of colic/laminitis
-Normal for some to reach, but don’t want a large amount to reach
What are the proteins in the hindgut?
-Expect most protein to be digested & absorbed into small intestine, but some can reach the hindgut
-Source of Nitrogen for the microbes, plus microbes utilize urea recycling to the hindgut
What are the functional sections of the equine hindgut?
-Cecum, ventral colon, dorsal colon, small colon
-Two important areas of size and reduction
What are the 2 important areas for size and reduction in the equine hindgut?
-Pelvic flexure
-Junction of small to large colon
What are the haustra?
-Saclike invaginations in cecum & colon
-Exist in hindgut of horse
-Bands of smooth muscle
When does soluble digesta reach the cecum in hindgut fermenters?
-~2 hours after ingestion - solids take longer depending on particle size
Every _____ there is mass movement contraction to move digesta from cecum to right ventral colon via cecocolic orifice
-Every 3-4 minutes
Is there retrograde movement from the colon back into the cecum?
-No
What aids in colon motility?
-Haustral segmentation contractions
-Propulsive peristalsis
-Retropulsive peristalsis
What do haustral segmentations contractions do for colon motility?
-Mix to promote fermentation & aid in VFA absorption
What is propulsive peristalsis in the colon?
-Originates near cecum following mass movements - propers digesta towards left ventral colon (moving things toward the end of the small intestine)
What is retropulsive peristalsis in the colon?
-Antiperistalsis movements in the left ventral colon resist digesta flowing forward -> results in retention & mixing
What is important about the pelvic flexure in the colon?
-Narrow diameter + antiperistalsis movements help to retain larger particles for further fermentation
-Allows liquids & soluble materia to pass through
Actions in the dorsal colon ____ those of the ventral colon
-Mimic
What creates impedance to digesta flow in the colon?
-Diameter decreases at junction of large & small colon
-Retropulsion originates near junction, which causes mixing & allows more fermentation
The pelvic flexure is a common site for
-Impactions
Segmentation contractions of the small colon form
Fecal balls
It is essential to buffer VFAs produced during fermentation why and how?
-Bicarbonate & phosphate buffers secreted from ileum, cecu & colon
-Essential to maintain pH
Along with electrolytes & bicarbonate, ____ is secreted in large quantities from colonic crypts during periods of high VFA production
-Water
-Water is reabsorbed as VFAs are absorbed across the epithelium
How is VFA absorption in the hindgut?
-Process identical to rumen
-Sodium accompanies VFA absorption, water follows
-Bicarbonate generated during this process
The small colon recovers
-Water
-Electrolytes
-VFAs
Large water & electrolyte fluxes in the large & small colon results in
high vulnerability of horses to colonic diseases -> fluids & electrolyte losses can be significant
Overall, transit through colon takes ____ in hindgut fermenters
2-3 days
As microbes die in the hindgut, what happens?
They are washed out & excreted in feces -> this is wasted microbial protein!
There is a limited utilization of ____ produced in hindgut - limited time for absorption
VFAs
Hindgut fermentation ____ efficient compared to ruminant foregut fermentation in terms of utilizing fermentation products
Less efficient
