Lecture 17: Non-Ruminant Herbivore Digestive Physio (Exam 2) Flashcards
What are pregastric fermenters & what are the two groups
- Fermenting prior to gastric stomach & SI
- Ruminants
- Non-ruminant herbivores (foregut fermenters)
What are some examples of fermenters
- Sheep
- Cattle
- Goats
- Deer
- Camels
What are hind gut fermenters (non-ruminant herbivores)
- Fermenting after SI
- Cecal fermenters
- Colon fermenters
- Limited absorption of products
What are some examples of cecal fermenters
- Rabbits
- Guinea pigs
- Chinchillas
- Rats
What are some examples of colon fermenters
- Horses
- Gorillas
- Elephants
- Rhinos
- Koalas
What is the diff btw/ pre & post fermenters
- Pre - The ruminant hangs on to material & get as many products as possible from digesta
- Post - Cecum &/or colon is huge
T/F: Whether the animal ferments Before or after the gastric stomach & the SI has a huge effect on efficiency of utilization of fermentation products
True
What does there need to be for microbial fermentation
- Retain digesta & microbes for long periods of time (sort & keep large particles)
- Maintain an envi suitable for fermintation
What 3 factors are needs for utilizing microbial fermentation
- Volume ava for fermentation (~ 75% of GIT derived to fermentation)
- Longer retention time for more fermentation & more contact time w/ microbes
- The microbial populations are very similar in different species
What are some GIT modifications to facilitate microbial fermentation for pre gastric animals
Have compartments in the stomach to selectively sort & retain fibrous material
What are some GIT modifications to facilitate microbial fermentation for hind gut animal
Either have a larger cecum &/or larger colon
What are the three categories of non-ruminant herbivores
- Foregut
- Cecal
- Colon
What is the difference in cecal & colon fermenters
Colon fermenters have a large cecum & colon while cecal fermenters only have a large cecum
Describe the compartmentalized stomach of a foregut fermenter
- One or more pouches for fermentation that is separate from the gastric region (pre gastric fermentation)
- 2 to 4 pouches for fermentation
- An expanded cardiac region for fermentation
What categories foregut fermenters be broken into
- Bulk roughage feeders
- Browsers
What foregut fermenter is a sloth
Browser
What foregut fermenter is a colobus monkeys
Browser
What foregut fermenter is a kangaroos & wallabies
Browsers & grazers
What foregut fermenter is a hippos
Bulk roughage
T/F: There are some non-ruminant herbivore domesticated species are foregut fermenters
False there are none
What is an advantage of being a foregut fermenter
Degrade plant toxins more easily
Describe a sloth stomach
- 3 chamber stomach
Describe a kangaroo stomach
- Not really chambered
- A long tubullar stomach w/ a sacciform, tubiform for fiber digestion, & fiber part of the stomach
Describe a colobus monkey stomach
4 pouches or chambers
What has to happen since the cecum is a bling sac
- Digesta must pass out via route of entry
- Allows the cecum to selectively retain certain fraction of feed
How many times a day do cecal contents enter the colon
1 to 2
Describe fiber digestion in cecal fermenters
- Digestion of fiber is low
- Seperation of particles based on density in colon
What happens to less dense material in cecal fermenters
- large fiber particles remain in the lumen
- Move on through the colon
What happens to smaller dense material in cecal fermenters
- & fluids
- Remain around the perimeter (proteins & easily digestible fiber)
- Move into the cecum for fermentation
Describe hard feces from cecal fermenters
Has indigestible fiber
Describe soft feces from cecal fermenters
- Night or cecotropes feces
- Cecal contents coated w/ mucus
- Consumed by animals b/c this stuff is coming from the cecum & has lots of B vitamins & microbial proteins (from microbes & dead microbes)
What are the major functions of the hindgut
- Primary site of microbial fermentation in colon fermenters
- Mixing of contents to promote fermentation & expose content to the mucosal surface to help w/ absorption of VFAs (controls pH)
- Ileum & colonic epithelium secrete bicarbonate (Helps to buffer the VFAs to control pH)
- Reabsorb fluid & electrolytes
T/F: Ruminants don’t really use their hindgut
True
What products of fermentation are used for energy (list the 3 main ones)
- Volatile Fatty Acids (VFAs)
- Acetate
- Propionate
- Butyrate
Why is there an enlarged colon & cecum for microbial fermentation in colon fermenters
- To ferment material that resists breakdown in the SI AND starch/sugar that escapes SI digestion
Why is hindgut fermentation less efficient than ruminant/foregut
- B/c there is less opportunity to absorb VFAs
- Can’t utilize microbial protein
What kind of subrstrates reach the hind gut
- Structural & non structual carbs
- Proteins
How much structural carbs reach the hind gut
- Acid exposure from the gastric stomach helps increases susceptibility to microbes
- The more structural carbs there is the more diff to digest (b/c of the cell walls)
- ALOT
How much non structural carbs reach the hind gut
- How much reaches the hindgut affects the risk of collic & laminitis
- When 30% is reaching the hindgut = dangerous
How much proteins reach the hind gut
- Some will reach but most absorbed in the SI
- Source of N for microbes
- Microbes reutilize urea recycling to the hindgut
What are the functional sections of the equine hind gut
- Cecum
- Ventral & dorsal colon
- Small colon
Where are two impt areas of size reduction in the equine hindgut
- The pelvic flexure
- Junction of large to small colon
What are haustra
- Bands of smooth muscle impt for contractions
- Saclike invaginations in the cecume & colon
- Cont. contract & expands to mix and expose digesta to fermentation
Why is cecal motility impt in the equine hindgut
- Mixes & slowly transports from haustra to haustra
- Keeps everything @ a good pace
- Every 3 - 4 mins mass movement contractions move digesta from the cecum to the right ventral colon via cecocolic orifice
What are the functional sections of the equine hindgut
- Cecum
- Ventral colon
- Dorsal colon
- Small colon
What is the haustra
Saclike invagination in the cecum and colon
T/F: Soluble digesta reaches the cecum ~ 2 H after ingestion while solids go through faster depending on the particle size
False; Solids take longer
What mixes & slowly transports from digesta from haustra to haustra
Cecal motility
How does digesta move from the cecum to the right ventral colon
The cecololic orifice
What are some ways the colon moves
- haustral segmentation contractions
- Propulsive peristalsis: Originates near the cecum following mass movements to propel digesta towards the left ventral colon
- Retropulsive peristalsis: Antiperistalsis movements in the left ventral colon to resist digesta flowing forward that results in retention & mixing in equine
Describe the movement of digesta through the pelvic flexure
- Narrow diameter + antiperistalsis movements help to retain larger particles for further fermentation
- Allows liquids & soluble material to pass through
What are the actions found in the dorsal colon
- Mimic the ventral colon
- Diameter decreases @ jxn of large & small colon which creates impedance to digesta flow
- Retropulsion originates near jxn which causes mixing & allows more fermentation
What is a common site for impactions
near or w/in the pelvic flexure
What causes fecal balls
Segmentation contractions of the small colon
Describe the small colon
- Recovers water, electrolytes, & VFAs
- Large water & electrolyte fluxes in the large & small colon results in high vulnerability of horses to colonic disease where fluid & electrolyte losses can be significant
Give a summary of hindgut fermentation
- Overall transit through the colon takes 2 - 3 D
- As microbes die in the hindgut they are washed out & excreted in feces (this is wasted microbial protein)
- Limited utilization of VFAs produced in hindgut (limited time for absorption)
- Hindgut fermentation is less efficient compared to ruminant foregut fermentation in terms of utilizing fermentation products
