Fermentation Flashcards
In hindgut fermenters, where does the fermentation occur?
Caecum, colon
Define fermentation, includes what the microbes provide enzymes for.
The metabolic action of bacteria, fungi and protoza. Microbes provide enzymes for hydrolysis of large molecules.
How does fermentation differ to monogastric in terms of speed, alteration of substrates?
Slower than glandular secretion, substrates are altered to a much greater degree
Why have vertebrates created a symbiotic relationship with microbies?
Because they do not produce cellulases (to break down cellulose)
What % of DM is digested by bacteria?
70-80%
What factors does microbiome composition vary with?
Diet, age, species, habitat
What ions are contained in saliva, and what is their function?
Bicarbonate (HCO3-) and phosphate ions (PO4)3-, they buffer VFAs acidity
what is the pH of the rumen?
6-7
What can be the cause of a lower rumen pH
Grain fed animals
Why do grain fed animals usually have a lower rumen pH
As the feed has a higher digestibility, more VFAs are produced, decreasing pH
List the products of pyruvate (post-glycolysis) in fermentation.
Acetate, propionate, butyrate, H+, gases (CH4, CO2)
List the order of acidity of the 3 main VFAs
Most: acetate
Middle: propionate
Least: butyrate
Categorise ‘simple sugars’, ‘starch’ and ‘cellulose’ into soluble, storage and structural CHOs (and list their speed of digestion - fast, middle, slow)
Soluble: simple sugars (fast)
Storage: starch (middle)
Structural CHO: cellulose (slow)
What % of VFAs are absorbed from rumen-reticulum
70%
Of the remainder 30%, what % of is absorbed from the omasum
60-70%
Are VFAs more easily absorbed in a dissociated or undissociated state?
Undissociated
What does carbonic anhydrase catalyse to produce?
Produces carbonate and H+
What products are produced from the deamination of amino acids
Ammonia (NH3) and VFAs
List 3 non-protein nitrogen sources that ruminal microbes can synthesise microbial protein
Ammonia, urea, nitrates
Where do ruminants recycle nitrogen from?
Ammonia, absorbed from deamination of protein in the rumen
Name the 2 basic patterns of reticulorumen motility
Primary (mixing) contractions
Secondary (eructation) contractions
Describe the primary contractions of the reticulorumen
Circular movement of ingesta in dorsal/ ventral sacs that moves denser material over cranial pillae
How often do secondary ‘eructation’ contractions occur?
Every other primary contraction, immediately after
What is the result of the eructation contractions?
Gas entering oesophagus and being eructated
List the order of the primary mixing contractions of the reticulorumen
PARALLEL contraction of reticulum
CAUDAL moving contraction of DORSAL sac
CAUDAL moving contraction of VENTRAL sac
CRANIAL moving contraction of DORSAL sac
CRANIAL moving contraction of VENTRAL sac
Describe the process of the secondary (eructation) contractions?
The dorsal blind sac has a cranial moving wave, which forces the gas cap cranially. The cranial sac relaxes and cranial pillar elevates so liquid ingesta moves away from cardia. This allows gas to enter the oesophagus.
How often to primary/ mixing contractions occur?
every 1-3 minutes
With the afferent and efferent fibres in the vagus nerve, what do the receptors monitor in regards to control of rumen?
Monitor distension, pH, concentration of VFAs, osmolality, tension receptors
Name the 4 rumen zones.
Gas cap, rumen mat, slurry zone, liquid zone
