Exam 4 (Lecture 47) - Foregut Fermentation I Flashcards
Describe the properties and functions of ruminant saliva.
Comes from parotid, mandibular, and sublingual salivary glands.
Isotonic, bicarbonate-phosphate buffer secreted in large quantities (100-200L per day)
Necessary for neutralizing acids formed by fermentation in the rumen
Describe the microscopic anatomy of the rumen where VFA absorption occurs.
Composed of numerous papillae that vary in size and shape
- from short and pointed to long and foliate
- aids in ruminal absorption
- SSE with keratinizes stratum corneum
- keratinized SSE
- numerous blood capillaries within the lamina propria
The rumen is composed of numerous ________ that vary in ________ and _________. What is the function?
Papillae; size and shape
Function:
- Absorbs a large portion of the VFAs
- Water and electrolytes are also absorbed here
Describe VFA absorption from the rumen to the blood capillaries located in the lamina propria.
Vacuolated, keratinized cells of the stratified squamous epithelium of a papilla.
Initially absorbed through the stratum corneum and passed cell to cell by way of intercellular channels to the cells of the stratum spinosum and stratum basale; then the absorbed substances are passed into the intracellular spaces before entering the capillaries.
Cells of stratum spinosum and stratum basale are metabolically active.
Because of the intercellular channels, absorbed solute can be transferred directly from the outer keratinized cells to the deeper metabolically active cells.
Where do VFAs come from?
VFAs are the byproducts of microbial fermentation.
What happens if VFAs are allowed to accumulate?
They will suppress fermentation.
Why are VFAs important for the cow?
They are important energy substrates for the cow
- they supply 60-80% of the dietary energy to ruminants
Which VFAs stimulate papillary growth?
Butyrate and Propionate
List the requirements that must be met by the cow for normal fermentation to occur.
1) Production of copious amounts of saliva
2) Microbes (rate of removal must be compatible with regeneration times)
3) Substrate for fermentation must be supplied
4) Temperature must be maintained at or near 37 degrees C
5) Moisture
6) Ionic strength (osmolality) of the rumen fluid must be kept within an optimal range (near 300 mOsm)
7) Negative redox potential must be maintained
8) Acid products of anaerobic fermentation must be buffered or absorbed
9) Normal motility patterns of the reticulorumen
10) Indigestible waste (solid material) must be removed
Describe the two patterns of reticulorumen motility.
1) Primary (mixing) Contractions
- biphasic (double contraction of the reticulum) when this phase begins
- first contraction is weak; second is extremely forceful and creates a rapid flow of fluid ingesta
- material enters cardia > caudal moving contraction of dorsal sac > cranial moving contraction of the dorsal sac > contractions of ventral sac > contraction of cranial ventral sac > back to reticulum
- figure 8 pattern of contraction
2) Secondary (eructation) Contractions
- occur with every second or third set of primary contractions
- consist of cranial moving wave that starts in the caudal-ventral blind sac and continues over the dorsal sac
- forces gas toward the cranial part of the rumen
- contraction of caudoventral blind sac expresses trapped gas into the dorsal sac
- cranial sac relaxation and cranial pillar elevation allow gas to enter the esophagus and be eructated
Name the 4 zones in the rumen. What type of material is in each zone? What happens to particle density (specific gravity) from dorsal to ventral?
1) Gas Zone
- gas
2) Solid Zone
- fiber mat
3) Slurry Zone
- mixture of solids and liquids
4) Liquid Zone
- liquids
From dorsal to ventral = low to high particle density
How do the physical characteristics of feed impact digestibility?
Digestibility is decreased by chopping or grinding feed
- b/c the duration of exposure to microbes is reduced as a result of rapid passage of feed thru rumen
Forage material of relatively high digestibility has a rumen 1/2 life of around 30 hours
Forage material of relatively low digestibility has a rumen 1/2 life of up to 50 hours
