Exam 3: Lecture 31 - Ruminant Digestive Physiology 1 Flashcards
How does the ruminant digestive strategy allow protection from predators?
-Ingest enormous quantities of forage in a short time, thus minimizing exposure in the open
-Spend maximal time ruminating in the protection of trees & rocks
What is/are the forestomach of the ruminant?
-Rumen
-Reticulum
-Omasum
What is/are the gastric stomach(s) of ruminants?
-Abomasum
What is important about the epithelium of the forestomachs of the rumen?
Stratified squamous epithelium
-No glands
-Pillars & papillae
How is pre-gastric fermentation accomplished in ruminants GIT?
-By microbes (bacteria, protozoa, fungi)
What is the overall capacity of the ruminant GIT?
-60-80 gallons
_____ have no omasum
-Pseudoruminants
What are the ruminants energy source?
-From VFAs
What are horses energy source?
-Starch digestion in SI + some VFAs from hindgut
What are the ruminant species?
-Cattle
-Bison
-Sheep
-Antelope
-Goats
-Deer
-Elk
Rumination = _____ + ______
-Rumination = regurgitation + remastication
How is microbial fermentation accomplished?
-Bacteria
-Fungi
-Yeast
-Protozoa
(Bacteria & protozoa are the biggest ones!)
Ruminants chew _______ times/24 hours
30,000-50,000
Where are the nasolabial glands located in bovine?
-Dermis of muzzle
What are the major salivary glands of bovine?
-Parotid (produces serous)
-Mandibular (produces mixed)
-Sublingual (produces mixed)
Is mucus thick or thin when talking about salivary glands and why?
-Thick b/c lots of glycoproteins
How much saliva is produced per day?
-40 gallons (~150 liters) on average per day
The amount of saliva produced per day depends on
-Size of animal
-Type of food
-Water already in food
What is the composition of saliva?
-Bicarb (important for buffering)
-Urea
-K
-Phosphate
-Cl
What are the functions of saliva?
-Buffering
-Add moisture
-Lipase (little bit)
What environmental conditions are needed to support fermentation?
-Appropriate substrate
-Temperature around 37 C
-Osmolality near 300 mOsm
-Anaerobic conditions
-Frequent mixing of ingesta
-Particle size reduction
-Indigestible material removal
-Synchronized movement of fermented content to intestine
-VFA must be buffered to maintain neutral pH
Why is appropriate substrate needed to support fermentation?
-Need to also feed the microbes in the rumen (not just feed the animal)
-Need energy & Nitrogen
-Starch, cellulose, Protein/N (urea)
How do we get frequent mixing of ingesta to support fermentation?
-Rumen motility (need normal rumen contractions)
What is an example of indigestible material removal?
-Lignin (associated w/ cellulose)
-More lignin in grass/hay, the less even cellulose can be digested
What is the primary site of fermentation in ruminants?
-Rumen
-60-75% of digestion
Does the rumen ferment cellulolytic or amylolytic bacterial species?
-Primarily cellulolytic
Cellulolytic bacterial species prefer ______ while amylolytic bacterial species prefer ______
-Cellulolytic = grasses/plants
-Amylolytic = starch/sugars
What are the end products of rumen fermentation?
-Acetate
-Propionate
-Butyrate
What do the end products of rumen fermentation serve as?
-Energy sources to the animal
There is more ____ produced by rumen fermentation on a fiber diet, while more ____ is produced by rumen fermentation on a grain diet
acetate, fiber (acetate is still the largest produced)
What are the by-products of rumen fermentation?
-CH4, CO2, heat
What do the papillae & extensive capillaries of the rumen do?
-Increase surface area
-Size varies
-Absorb VFAs (stabilize rumen pH)
What do the muscular rumen pillars do?
-Help w/ contraction occurring b/c squeeze together & help area mix well
What do the muscular pillar and folds of the rumen do in mixing?
-Help divide rumen into different areas
Where does the primary contraction start in ruminants?
-Starts in reticulum & moves caudally
____ has a honeycomb appearance
Reticulum
What is shown?
Reticulum
What are the major functions of the reticulum?
-Form bolus for regurgitation (when animal lays down to ruminate)
-Move particles to the omasum (typically small enough to exit the rumen)
-Move particles to rumen (b/c need to retain larger particles for more rumination to occur)
What disease can happen in the reticulum?
-Hardware disease (bovine traumatic reticuloperitonitis)
-Reticulum sits a bit lower than rest of rumen, so things fall here
Material from the rumen passes into the omasum via the _____
-Reticulo-omasal orifice
What part of the ruminant stomach has “many plies”?
-Omasum
What does the omasum do?
-Regulates passage of digesta into lower tract
-Some absorption of water & VFAs
Which stomach compartment is the gastric stomach with many folds?
-Abomasum
What does the abomasum do?
Gastric glands to secrete HCl
-Acidity kills microbes washing in from rumen - starts digestion
-Microbes provide protein (essential AA) to the animal)
Secretion of pepsinogen
-Hydrolyzes microbial & dietary protein
There are about ____/minute abomasal contractions
2-3/minute
Why are abomasal contractions important?
-Mixing, material exits to SI, and drive gas back to rumen
-Have a lot of CO2 dissolved in rumen fluid that becomes liberated to free gas when meets acid in abomasum (free gas build up in abomasum = bad)
Rumen forages contain
-Cellulose
-Hemicellulose
-Sugars
-Starch
-Protein
-Lignin
What are examples of rumen forages?
-Grass, hay
-Legumes
-Brush & weeds
-Silage
-Byproducts - i.e. corn stalks, citrus pulp, peanut straw
Concentrates (grain) contain mostly
-Starch
-Protein
-Sugars
What are some examples of concentrates (grain)?
-Grain
-Soybean meal/whole soybeans
-Other seed meals
What is rumen fermentation?
-Microorganism-mediated transformation from one nutrient compound to another
-Ex: taking cellulose & producing acetate
-Ex: taking starch & producing propionate
What do microflora do?
-Attach & grow on the substrate, utilize metabolites & secrete metabolites
What are the rumen microflora?
-Bacteria
-Protozoa
-Fungi
Primarily feed the ____ - then the ____
Primarily feed the flora - then the cow
What happens to the dead rumen microbes?
-Dead microbes flow to intestines and are digested
What are the rumen layers from bottom to top?
-Small high-density particles
-Liquid
-Fiber mat (provides scratch factor - everything in this layer has large, low-density particles)
-Gas layer (want it near the esophagus so the cow can eruptate)
What products undergo fermentation in the rumen?
-Monosaccharides
-Disaccharides
-Starch
-Cellulose
-Other sugars
What is the % of carbohyrates fermented in rumen to short chain (volatile) fatty acids (VFAs)?
-60% Acetate -> higher with forage diets
-30% Propionate -> higher with grain diets
-10% Butyrate
Sugars -> _____
VFA
Starch -> ____ -> _____
Starch -> glucose -> VFA
Cellulose -> _____ -> _____
Cellulose -> glucose -> BFA
Lignin -> ____
Undigested (microbes can’t deal with)
Ruminants use ___ for energy
VFA
Ruminants have a lower ____ than most non-ruminants
Blood glucose
How does gluconeogenesis work in ruminants?
-Use propionate (from fermentation) to make glucose
Fat synthesis in ruminants uses
Acetate
Most acetate is transformed to ____, and most propionate is used to _____
Fat, most propionate is used to make glucose
Proteins are fermented to
-Peptides
-Amino Acids
-Ammonia (a lot converted to this)
-Branched-chain VFAs
_____ use protein components and metabolites in synthesizing cell wall & cytoplasmic proteins
Microbes
Where are dead microflora digested?
-Small intestine
____ provide the highest quality protein possible
Microbes
-They contain essential amino acids the animal needs
T/F: You can feed low quality proteins or metabolites (urea) & cow absorbs highest quality amino acids from small intestines
TRUE!
-Cow will still be fine b/c will get essential AAs from microbes
There is major ____ cycling in ruminants
Urea
___ is produced in the rumen from protein fermentation
Ammonia
What happens to ammonia produced in the rumen from protein fermentation?
-Immediately utilized by microbes OR absorbed & converted to urea by liver
What are the fates of urea in ruminants?
-Excreted by kidney
-Recycled to saliva*
-Recycled to rumen*
What are the components of rumen motility?
-Primary contractions
-Secondary contractions
-Reticular contractions
Explain the primary contractions in the rumen
-Major coordinated movements cranial to caudal primarily for mixing
-About 2 per minute
Explain the secondary contractions in the rumen
-Caudal to cranial primarily to eructate gas (pushing gas into esophagus)
Explain the reticular contractions in the rumen
-Associated w/ cud chewing
-Help form bolus & bring it to esophagus for regurgitation & rumination
What is the importance of rumination?
-Reduces particle size
-Increases surface area
-Adds saliva
Particles need to me ____ to pass from the rumen
< 1 mm
What are the 4 main components of rumination?
-Regurgitation
-Reinsalivation
-Remastication
-Reswallowing
Explain regurgitation in rumination
-Initiated by reticular contraction AND relaxation of distal esophageal sphincter
-Allows bolus to enter esophagus & go to mouth and remastication, reinsalivation, etc. occurs
When does rumination happen?
-Occurs when animal is resting (laying down)
-Begins 30-90 minutes after eating (usually)
-Ruminate up to 10 hrs/day (will not ruminate as much on a high grain diet)
How is the process of rumination initiated?
-By an “extra” contraction of reticulum that pushes ingesta into the area of the cardia
What is the process of rumination?
-Distal esophageal sphincter opens
-Inspiratory excursion w/ glottis closed causing negative pressure in intrathoracic esophagus
-Bolus of ingesta moves into esophagus
What does reverse peristalsis do?
-“Vomits” bolus into mouth
What happens during reinsalivation, remastication & reswallowing?
-Fluids are squeezed out of bolus & swallowed, ingesta chewed & additional saliva added
-Cud swallowed & process repeated
-Process is a complex reflex control mediated by medulla
What provides the “scratch factor” and why is this important?
-Epithelial receptors in the reticulum provide this
-Important to provide large enough fiber so they can get this “scratch factor”
What is the ideal pH for the rumen environment?
-6.8
Which VFA is used by ruminants for fat synthesis?
-Acetate
