Lecture 26: Forestomach Fermentative Digestion-1 Flashcards
What is fermentation
Metabolic processes performed by microorganisms that converts carbohydrates to acids, gases and/or ethanol
What plant component must be broken down by microbial fermentation
Fiber (cell wall)
What are the 3 carbohydrates from plants
- Fiber (cell wall)
- Sugar (cell content)
- Starch (endosperm)
What is crude protein composed of
Proteins and non-protein nitrogen sources
What is the role of non-protein nitrogen sources for the microbes and for host animal
NPN use urea, salts, ammonia, etc that can supply nitrogen to microbes and build microbial protein.
- Supplies the microbes
- Microbes are large source of protein to host animal as they get digested and sent to SI
Fats are added to ruminant diets as they are essential for fermentation but have negative effects on ___ and ___
Milk production and rumen fermentation
What are the 3 substrates needed for microbial fermentation
- Carbohydrates
- Proteins
- Fats
Which is slower glandular digestion or fermentation
Fermentation
What are the fast fermenting carbohydrates
Sugars from the cell wall are easily digestible by both pancreatic enzymes and microbes
What carbohydrate is fermented down 2nd fastest
Starch from endosperm
What carbohydrate takes the longest to ferment and how long does it taken
Fiber takes around 2-3 days (60-70hrs)
___ movement/ ___ transit times facilitate reaction time in fermentation process
Slow, long
What are the fermentation chambers in foregut fermenters
Pre-stomach chambers
What are the fermentation chambers in hindgut fermenters
Colon and cecum
How long does glandular digestion take
Very fast 2-3hrs
How fast does fermentative digestion take
Variable (fast to slow) ~2-3 days
Slow due to fiber fermentation
How does the space in the stomach compare in glandular vs fermentative digestion
Stomach in glandular digestion is fairly small and fermentative chamber is large
What substrates are used in glandular digestion
Carbohydrates, proteins and fats
What substrates are used in fermentative digestion
Carbohydrates, proteins, fats, non-protein nitrogen
What are the end products of glandular digestion
Mono, di and tri peptides, monosaccharides, Micelles
What is the end product of fermentative digestion
VFA, microbial protein and gases
Describe the microbial ecosystem in the GI track of cattle
- Cattle consume feed
- Rumen microbes break down feed
- Microbes grow
- Microbes produce byproducts including energy as VFA and protein
- Regulate rumen environment
What do microbes produce as byproducts
- VFA
- Proteins
Microbes initiate degradation of ___, ___ allele chemicals and soften certain substrates
Cellulose, detoxify
Microbial waste products are ___ used by mammalian host
short chain fatty acids
The microbes are ___ by mammalian host and provide microbial protein
Eaten
What is the largest proportion of microbe in rumen and hindgut
Bacteria
What do bacteria do in rumen and hindgut
Fiber fermentation and enzymatic break down of carbohydrates
What do fungi do in rumen and hindgut
Cellulose activity
What do Protozoa do in rumen and hindgut
- Ferment fiber
- Ingest bacteria (regulate growth)
- Slow digestion of rapidly fermenting starch by ingesting/storing
What microbe in rumen and hindgut regulates bacterial growth
Protozoa
___are the end product of anaerobic microbial metabolism
VFA’s
What do VFA’s do to pH and how does the body respond
Lower pH, but is buffered by saliva which has bicarbonate in it
What breaks down pyruvate to acetate and butyrate
Acetyl-CoA
Pyruvate break down results in production of __
VFA
What breaks down pyruvate to propionate
Lactate and succinate
What breaks down pentoses to acetate
Acetylphosphate
Microbes are ___specific
Substrate
What microbe species are involved in fermentation breakdown to VFA’s
Cellulolytic, hemicelulolytic, pectinolytic
What microbe species break down organic polymers (cellulose, starch, hemicelluose) to soluble sugars
Amylolytic species
What microbe species produce methane in fermentation process
Methane producing species
What microbe species produce acetate in fermentation process
Acids utilizing species
What is VitB12 essential for
Cell growth and maturation, brain development, blood synthesis and epithelial repair in GI tract
What is another name for vitamin b12
Dietary Cbl
How is vitamin b12/dietary Cbl transported normally
- Dietary Cbl bound to R proteins and intrinsic factor
- R protein is secreted b saliva, gastric cells and pancreas
- IF secreted by parietal cells - R protein is digested in duodenum and the released Cbl forms more IF-Cbl complexes
- In ileum the IF-Cbl complex is recognized and the Cbl is absorbed by endocytosis
What secretes R protein
Saliva, gastric cells and pancreas
What secretes IF
Parietal cells
How is B12 supplied to animal
Diet and/or microbial production
Where is Cbl stored and for how long
Liver and muscle store Cbl for a few weeks
What can cause damage to the supply of B12
- Insufficient dietary
- Insufficient transport proteins (R and F)
- Reduced microbial production due to cobalt deficiency in diet of ruminant **microbes produce B12
What can cause a reduction in R protein or IF production therefore resulting in B12 deficiency
Inflammation in stomach or SI
Ruminant microbes can produce B12 but must be supplemented for __
Cobalt
What is the equation for microbial yield
Mass of microbial dry matter/mass of substrate needed
A high microbial yield provides an important ___source for ruminant
Protein
Yield is affected by __, ___, ___ and __
- Temperature
- PH
- Dilution rate of rumen fluid
- C/N ratio in diet
What is dilution rate in microbial yield
Large saliva volumes stabilize pH and provide fluid for dilution
__protein is a major source of protein for the host
Microbial
What is the C/N ratio of feed for livestock
Carbon to nitrogen ratio of mass of carbon to mass of nitrogen
The is the C/N of vascular plants
> 20
Carbon to nitrogen ratios are an indicator for ___
Nitrogen limitation of rumen microorganisms
How does an increase C/N ratio affect microbial growth rate
Ample energy but insufficient nitrogen so the available energy is used by microbes for maintenance rather than growth
What does a decreased C/N ratio do to microbial growth rate
Ample N to support growth, but insufficient energy for maintenance, therefore available energy is used by microbes for maintenance rather than growth
Increased or decrease glucose/protein ratios will ___ the microbial yield
Lower
A matched glucose/protein ratio will ____microbial yield
Maximize
Where is urea formed
Liver
How is hepatic urea formed
Deamination of endogenous amino acids as well as from nitrogen absorbed as ammonium
Where is urea transported to
Liver
Urea is mostly excreted in urine but in ruminant urea can be ___ and returned to rumen via ___
Recycled, saliva
Urea adds to the ___source
Non-protein nitrogen source
Nitrogen flow to and from the rumen depends on ___
Rumen ammonia concentration
What happens to urea if there is high nutritional protein concentration
Causes high blood urea and much of it will be secreted in the urine
What happens to urea if there is low nutritional protein with high carbohydrate availability
Leads to low rumen ammonia availability and this will stimulate nitrogen flow to rumen
What stimulates nitrogen flow to the rumen
Low rumen ammonia
The nitrogen portion of urea is used as building block for production of ___ by ___
Protein by rumen microbes
What byproduct is released from urea
Ammonia
What are the two pathways for ammonia after released from urea
- Produce microbial proteins
- Liver where it is detoxified and excreted in urea
What can result from excess urea in diet
Overwhelm liver and toxicity can occur
Describe a closed system of microbial growth with lag, log, stationary and decline phase
- Lag: adjustment period after cells are initially cultured, nothing happens
- Log/exponential: cells start dividing and increase #
- Stationary
- Decline
Why does microbial growth decline in a closed system
Because nutrients exhaust and conditions (pH and oxygen) become unfavorable due to inability to remove waste
Is the rumen an open or closed system
Open
What does the rumens open system promote
Continuous growth of microbes maintaining cell population in log/exponential phase
Why/how is the rumen an open system
- Continuous feed input
- Gas released, VFA absorbed, buffers
- Movement of rumen contents (microbes, undigestible material, VFA microbial waste) into omasum
What are some ways in which the rumens open system can be damaged and cause it to enter stationary and eventually death phase
- Diet inappropriate
- Can’t get rid of waste
- Lack of buffers released in saliva, acidic
