Lecture 28: Forestomach Fermentative Digestion-2 Flashcards
Grazers or browsers: selectively feeding on highly digestible material
Browsers
What do grazers mainly eat
Grass
How do grazers and browsers handle the high concentration of tannins in their diet
Parotid gland produces proline-rich proteins which bind and neutralize tannins
Which has a larger parotid gland, browsers or grazers
Browsers
Browser or grazer: rumen content is not layered
Browser
Describe the rumen structure/contents of the browser
No fiber mat, no stratification allowing fora more homogenous distribution of particles
Browser or grazer: high viscosity fluid, separation due to floatation/sedimentation less possible, gas bubbles evenly distributed
Browser
Browser or grazer: low viscosity fluid: separation due to flotation sedimentation and clear separation of gaseous layer
Grazer
What stimulates rumen papilla growth
VFA’s
VFA concentration is highest where __activity is highest
Microbial
How does the distribution of the ruminal papilla differ in the grazer and browser
Browsers have a more evenly distributed rumen papilla, whereas the papilla are greatest at the fiber mat water boundary in grazers where microbial activity and VFA’s are highest
Where browsers have the most papilla and greatest absorption of VFA in the dorsal, atrium or ventral rumen
Evenly distributed throughout all 3
Where are the most papilla and greatest absorption of VFA’s in the grazer rumen, dorsal, atrium or ventral rumen
Atrium which is boundary between fiber mat and sediment
How does papilla size indicate activity in the rumen
Small papilla indicate decrease microbial activity and inappropriate pH, whereas large papilla indicates increase microbial activity
What epithelium layer are VFA’s absorbed through
Stratified epithelium
How does a long mean retention time affect utilization of fiber
Improves utilization of fiber
How does a long mean retention time affect feed intake
Restricts because the intake of roughage is limited mostly by the capacity of the forestomach
Who has a greater mean retention time of particle passages through the rumen, browsers or grazers
Grazers have greater retention time for food particles through the rumen to have time for microbial fermentation
Who has a longer fluid retention time in the rumen, grazers or browsers
Browsers
Why is it important for grazers to have a higher fluid throughput in the rumen
Water passing through rumen is needed to:
1. Wash out microbial proteins to SI to become available to calf (increase microbial yield)
2. Saliva contains bicarbonate buffer which will neutralize acidic rumen from VFA’s
3. Move sediment waste from the bottom that is taking up space
Why is food particle throughout in rumen faster in browsers
Rely more on cell wall content (carbs and proteins) which is easily fermentable, unlike grazers which need to ferment fiber
Removing waste and microbes stimulates ___growth by maintaining appropriate conditions in the rumen. This increases ___ yield from the forestomach
Bacterial, microbial
Maintaining rumen activity promotes what phase of growth
Log phase
What is quorum sensing
Mechanism by which bacteria through small signal molecules called autoinducers regulate population density so as higher densities bacteria stop reproducing and making microbial protein
What are the 2 functions of the omasum
- Absorption of water, electrolytes, VFA and bicarbonate
- Transport of ingesta to abomasum
What is the absorption of water so important in the omasum
Needs to dilute solution before entering abomasum in order to optimize activity in abomasum and maintain pH2-3
What is the function of omasal laminae
Surface extensions
Who has a greater water reabsorption, grazers or browsers and why
Grazers, because omasum is larger in size
Why does more water flow through grazers vs browsers stomachs
Helps remove waste and microbial protein and facilitates better fiber fermentation
What are the end products of microbial production of VFA’s by breaking down cellulose and starch
- Acetate
- Proprionate
- Butyrate
What are the two ways in which VFA’s can be absorbed
- At pH at 6.8 VFA exist in dissociated form via the VFA/bicarb exchanger
- Lower pH, closer pK are absorbed via diffusion
At what pH is VFA absorbed is dissociated form
6.8
At what pH is VFA absorbed in undissociated form
Low pH closer to pKA
What is the fate of acetate in the microbial production of VFA’s
Enter creb cycle as acetyl-CoA, form ATP and adipose tissue synthesis
What is the fate of proprionate in the microbial production of VFA’s
Enter creb cycle as Succinyl-CoA resulting in gluconeogensis
What is the main source of glucose in the ruminant and is important for milk production
Proprionate
What is the fate of butyrate in the microbial production of VFA’s
Converted to B-hydroxybuturate and enter creb cycle as Acetyl-CoA
How do cows help maintain pH and prevent rumen acidification
Saliva buffer with bicarbonate
What type of feed generates larger amount of VFA’s in short period of time
Easily digestible carbohydrates like grain
If the amount of VFA’s increase and lowers pH what microbes are favored and start producing what
Favored microbes producing lactic acid
Describe the steps that can lead to rumenacidosis
- Carb overload
- Increase VFA’s
- Decrease pH
- Decrease lactate users(enzymes that can utilize lactate to control pH)
- Increase lactate producers
- Increase lactate
- PH decreases further
Describe how an increase in VFA production can initially be beneficial but then is disadvantageous
1st 24hrs it will increase milk production and but then the low pH will not favor microbes that produce VFA’s but rather those that produce lactate acid and further decrease pH
Describe how the decrease in pH increases milk production initially in rumenoacidosis
Initially VFA’s will go into undissociated form and will follow concentration gradient down, creating more propionate—> gluconeogenesis and increase milk production but then pH is too low to promote microbes producing VFA’s
How can rumenacidosis cause variable appetite
Pain in rumen, decreased microbial activity
How can rumenacidosis cause a drop in milk production
Not enough VFA’s delivered to make proprionate and undergo gluconeogenesis
How can rumenacidosis cause diarrhea
Malabsorption because of the reduction of microbes
How can rumenacidosis cause bloat
Decreased food intake but still producing gasses
How does rumenacidosis increase breathing rates
Countermechanism to breathe off more CO2 to try and combat metabolic acidosis
How can rumenacidosis cause laminitis
Metabolic acidosis and endotoxins which are fragments of bacteria that enter blood stream
Where does glandular digestion begin
Abomasum
What is the role of lysozymes in the abomasum
Break glycosidic bonds of bacteria wall, specifically 1,4 beta-linkages between N-acetylmuramic acid and N-acetyl D-glucosamine
What component of the abomasum help to make use of microbial protein
Lysozymes
What % of dietary protein is rumen degradable vs % bypass protein
Rumen degradable: 70-80%
Bypass proteins (20-30%)
What is biological value
Measure for estimating how well a particular protein source is utilized
What is considered high value protein
Food that contains animo acids similar to that of the host (ex: fish meal)
What is downgrading of high biological value protein
Rumen degrades protein first via microorganisms and then used to resynthesizes bacterial protein that is available to animal (ex: fish meal)
What is upgrading low biological value protein
Bacteria are able to use NPN to produce microbial protein
What is the most important NPN
Urea
How is urea recycle
Via saliva into rumen for usage by bacteria which turn it into microbial protein
Why is adding chicken poop to diet a problem
Salmonella, Avian influenza
Where is urea recycled to in ruminants
Large intestine and rumen via saliva
Where is urea recycled in monogastric animals
SI and LI
Go ot LI for microbial digestion and go to SI just because it will eventually end up in large
What transporters are used in urea recycling
Aquaporins (SI and LI)
Urea transporter B (UT-B) (LI only)
Why is urea recycling important in hindgut fermenters
Salvage mechanism to improve nitrogen retention during times of protein deficits
What determines the amount of microbial protein that reaches the small intestine
Amount of dietary crude protein and metabolic demand
What determines plasma urea in a ruminant
Amount of microbial protein that reaches the small intestine in the presence of excess ammonia in rumen
How can urea poisoning/ammonia toxicosis
- Rumen microbes convert NPN to ammonia via urea
- Ammonia is then combined with keto acids by microbes to produce amino acids
- If the rate of ammonia production or ingestion of ammonia exceeds microbe ability to utilize and form amino acids there is accumulation of ruminal ammonia
- Ammonia is normally detoxified by the liver but accumulation can overwhelm liver resulting in neurological symptoms
What does ammonia do to ruminal pH
Exceeds 7.5–> alkaline indigestion
How does accumulation of ammonia and increase pH affect ruminal contractions
Inhibited
How does urea poisoning/ammonia toxicosis affect VFA,s microbial yield, milk or beef production
Decrease all
Excessive intake of ____ can cause accumulation of ruminal ammonia and decrease of VFA’s
Crude protein
What is a rumen drinker
Postnatal development of esophageal groove bypass reticulum to omasum, if this doesn’t happen then milk will spillover into rumen which is an easily digestible carbohydrate resulting in malfermentation
What happens to the ruminal lining in rumen drinkers and why
Milk not shunted to abomasum and ends up in rumen will be fermented to lactic acid and decrease pH, causing inflammation, irritation and thickening of rumen which affects ability to contract and absorb nutrients (malnutrition, bloat, acidosis)
What triggers formation of esophageal groove
Cephalic phase—>activation of PNS and milk let down
How does the absence of suckling/ drinking milk out of bucket cause rumen drinking postnatally
Doesn’t activate PNS and cephalic phase which triggers esophageal groove
How long do ruminants circumvent the rumen after birth
3 weeks
When does a ruminant reach full adult morphology for functional fermentation
8 weeks
