Lecture 31: Ruminant Digestive Physio 1 (Exam 3) Flashcards
What does the digestive strategy of ruminants all
- Protection from predators
- Ingest enormous quantities of forage in short time thus min exposure in the open
- Spend max time ruminanting in the protection of trees
What type of cells are found
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Describe the ruminant GIT
- Compartmentalized stomach in the order: rumen to reticulum to omasum to abomasum
- Pregastric fementation accomplished by microbes (protozoa, bacteria, & fungi)
What do pseudoruminants not have
An omasum
What are differences btw/ ruminants & non ruminant herbivores
- The site of fermentation
- Ruminants get energy from VFAs
- Horses get energy from starch digestion in the SI & some VFAs in the hindgut
List some ruminant species
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How do ruminants breakdown feed physically
- Prehension
- Mastication + eating
- Rumination (regurgitation + remastication)
- Microbial fermentation (bacteria, fungi, & protozoa)
What are the nasolabial glands
- Present on the dermis of the muzzle
- Very watery to keep the whole nose & mouth moist
What are the major salivary glands (produce majority of the saliva) in ruminants
- parotid
- Mandibular
- Sublingual
What type of salivation does each major gland produce
- Parotid - serous (watery)
- Mandibular & sublingual - mixed
What makes mucus salivation thick
Lipoproteins
How much saliva do ruminants produce
~ 40 gallons
What are the composition & functions saliva
- Made of: bicarb, urea, potassium, phosphate, & Cl
- Bicard is the most important for buffering the acid in the rumen
- Functions: buffering, add moisture to food (70% of all water in the rumen comes form saliva), & lipase
What envi conditions are needed to support fermentation
- Have to have an appropriate substrate (Have to feed the microbes in the rumen)
- Temp around 37
- Osmo near 3000 mosm
- Anaerobic conditions
- Need frequent mixing of ingesta (rumen motility)
- Reducing particle size
- Removal of indigestible material removal (like the removal of lignin)
- Synchronized movement of ferment content to the intestine (depends on particle size; the smaller particles can leave)
- VFA must be buffered & removed/absorbed (pH of 6.8)
What do microbes need to fxn
- Energy
- Nitrogen (from protein or urea)
What are appropriate substrates
- Starch
- Cellulose
- Protein/nitrogen (urea)
What is the primary site of fermentation
Rumen
What is the #1 type of microbe present in the rumen
Bacteria
What are cellulolytic bacterial species
Bacteria prefer action on grass
What are Amylolytic bacterial species
Bacteria that prefer starch & sugar
Describe the end products of fermentation in the rumen
- Acetate, propionate, & butyrate
- Provide energy to the animal
- Methane, CO2, & heat are by products of fermentation
- More acetate os produced overall on a fiber diet (grass); 65: 25: 10 ratio
- More propionate produced on a grain diet; 50: 40: 10
What is this
Papillae
Describe papillae found in the rumen
- Increase SA
- Vary in size
- Main fxn is to absorb VFAs (stabilize the rumen pH)
- Extremely impt in grain diets
Describe the muscular pillar & fold in the rumen
- Help divide the rumen in to diff areas
- Help w/ contraction by squeezing together
- Primary contraction start in the reticulum & moves caudally
- Contraction & mix -> relax -> repeat
What is the appearance of the reticulum
Honey comb
What are the 3 major functions of the reiculum
- Form bolus for regurgitation
- Move particles to the omasum (small enough particles exit the rumen)
- Move particles to rumen (larger particles)
What is an important prob that is associated to the reticulum
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How does the material from the rumen passes into the omasum
Via the reticulo-omasal orifice
What is this
Omasum
Describe the omasum
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Describe the abomasum
- Gastric stomach
- Lots of folds
- Lots of gastric glands that secrete HCL (acidity kills microbes washing them in from the rumen which provide proteins that are essential AAs)
- Secretion of pepsinogen - hydrolyzes microbial & dietary protein
Describe the abomasal contractions & their importance
- About 2 or 3 every min
- Mixing
- Material exits to the SI
- Drives gas back to the rumen: CO2 dissolved in the rumen fluid liberated when it meets acid in the abomasum
What does forage contain
- Cellulose
- Hemicellulose
- Sugars
- Starch
- Protein
- Lignin
What does concentrate (grain) diets contain
- Starch
- Protein
- Sugars
What are the micro organisms doing to the substrate in the rumen
- Attach & grow on the substrate
- Use metabolizes to grow & reproduce
- Secrete metabolites
List the layers of the rumen
- Bottom layer - small high density particles
- liquid
- Fiber mat - everything in this layer has large low density particles (provides “scratch factor”)
- Top layer - gases (near to the esophagus so they can be released)
What products are undergoing fermentation in the rumen
- Monosaccharides
- Diasccharides
- Starch
- Cellulose
- Other sugars
What are sugars fermented into
VFA
What is starch being ferment to
Glucose then into VFA
What is cellulose fermented into
Glucose -> VFA
Is lignin fermented/digestable
NO
Describe the blood glucose of ruminants
Lower blood glucose (60 mg/dl) compared to most non-ruminants (100 mg/dl)
What is used in fat synthesis (milk & body fatO
Acetate is used
What is the % of VFAs fermented from carbs
- 60% Acetate
- 30% propionate
- 10% butyrate
What are proteins fermented to
- Peptides
- AAs
- Ammonia
- Branched chain VFAs
When do microbes use protein
Use the protein components & metabolites in synthesizing the cell wall & cytoplasmic proteins
Where are dead microflora digest
The small intestine
What type of protein do microbes provide
- The highest quality protein
- Contain essential AAs the animal needs
Can cattle be fed low quality proteins (Lack essential AAs) or metabolites (urea)
- Yes
- Cows absorb the highest quality of AAs from the SI
Where is urea produced
The liver
T/F: There is minor urea recycling in ruminants
False: major urea recycling
What happens after ammonia is produced in the rumen (from protein fermentation)
It is immediately utilized by microbes or absorbed & converted to urea by liver
What are the fates of urea
- Excreted by the kidney
- Recycled to the saliva
- Recycled to the rumen
What is the primary contraction of the rumen
- Major coordinated movements cranial to caudal for mixing
- About 2 per min
What are secondary contractions in the rumen
Caudal to cranial primarily to eructate gas
What contractions are associated w/ cud chewing
Reticular contractions
Describe regurgitation
- Initiated by a reticular contraction & relaxation of distal esophageal sphincter
- Bolus enters the esophagus & goes to the mouth then is re chewed & ingested
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