L26: Forestomach fermentation digestion Flashcards
T/F: Fermentation is slower than glandular digestion
T
give an example of a rapidly ferementable carbohydrate and a slowly fermentable one
sugar is fast
starch is medium
fiber is slow
what is needed for optimal fermentation
- pH, moisture, ion composition, redox-potential
- slow movement/long transit times facilitate reaction time
- specific motility patterns
- continuous removal of waste products; release of gases
what are the fermentation chambers
- forestomach
- sub-region in stomach (ex: non-glandular region in horses)
- hindgut (colon & caecum)
end products of fermentation
- VFA
- microbial protein
- gases
rumen microbes are _____, they coexist with the mammalian host for mutual benefit
mutualists
microbes initiate the degradation of ______ and detoxify ________
cellulose
allelochemicals
what happens if VFAs accumulate in the rumen
they lower the pH but the buffer (saliva) & removal from fermantation chamber helps maintain pH and avoid rumen acidification
T/F: microbes are substrate specific
T
what are the ways in which animals acqurie B12
diet (dogs,cats,pigs) and or by microbial production (ruminants)
dietary Cbl (Cobalamin) is bound to what 2 proteins
R-protein and intrinsic factor (IF) forming complexes
what cells secrete intrinsic factor (IF)
parietal
where is R protein digested
duodenum
where can Cbl be stored
liver and muscle
what can cause insufficient Cbl levels / B12
- insufficient dietary Cbl
- insufficient transport proteins caused by inflammation in stomach / SI which reduces R protein and/or IF production
- reduced microbial production due to cobalt deficiency in the diet of ruminant
although ruminant microbes can produce B12, it has to be supplemented with ?
Cobalt
what is microbial yield
mass of microbial dry matter / mass of substrate
what things affect microbial yield
- temperature
- pH
- dilution rate of rumen fluid
- C:N ratio in diet
increased C:N ratio
- enough energy but insufficient N
- available E gets used by microbes for maintenance rather than growth
decreased C:N ratio
- ample N to support growth, but insufficient E for maintenance
- available E is used for maintenance rather than growth
increased or decreased glucose/protein ratios will ____ the microbial yield
lower
a matched glucose / protein ratio will ______ the microbial yield
maximize
urea is formed in the ______ & is an an important source for _____
liver
NPN
where does hepatic urea come from
- deamination of endogenous amino acids
- nitrogen absorbed as ammonium in rumen
urea is mostly excreted via ?
urine
but in ruminants, it can be recycled and partially returned to rumen via saliva
what does N flow to and from the rumen depend on
rumen ammonia concentration
effect of high nutritional protein concentration on blood urea
causes high blood urea; most of which is secreted in urine
how does low nutritional protein (w/ high CHO availability) affect the rumen
low rumen ammonia levels; stimulates nitrogen flow to rumen
the ______ portion of urea is used as the building block for the production of protein by rumen microbes
nitrogen
ammonia released from urea can go either of what 2 pathways
- production of microbial protein
- to the liver where it is detoxified and excreted in urine
in a ______ system, microbial growth is characterized by 4 phases: lag, log, stationary and decline
closed
why does microbial growth decline in a closed system
nutrients get exhausted and conditions (pH, Oxygen) become unfavorable
the rumen is mostly an _______ system, so microbial growth is continuous
open
maintains cell population in exponential growth for long periods of time
what makes the rumen an open system
- feed input
- gas release; VFAs absorbed
- movement of rumen contents into omasum
what makes the rumen not an entirely open system
no - little oxygen
where in the GI tract is the IF-Cbl complex absorbed by endocytosis
ileum
what is dilution rate
large saliva volumes stabilize pH & provide fluid for dilution
what are the sources of nitrogen
- protein
- urea
- ammonia
- nitrate
what is a major protein source for the host
microbial protein
does urea contain any E, minerals or vitamins
no
why might excess urea be bad
can overwhelm liver and cause toxicity
