Midterm Material Flashcards
what is rumination chewing
more slow and even chews which reduces particle size which is important for ?
chewing stimulates? and why is it important?
bicarbonates…
Salivary Glands
Parotid, Mandibular, Sublingual, others
– Saliva production with 50% produced by parotids
Saliva made up of
water primarily plus ions
(Na, K, Cl, bicarbonates, phosphates), enzymes
(lysozyme, lipases), and mucin
Saliva has digestive functions
Solubilizes (dissolves food) to aid in tasting food +
to start digestion of food
• Lubrication to aid in Mastication (chewing),
rumination, and swallowing
– Role of mucus for bolus formation to facilitate swallowing
• Role of amylase for starch digestion in specific
species but not ruminants
Source of buffers + nutrients &mode for waste excretion
– Buffers acidic foods in all species and buffers volatile
fatty acids (VFA) produced in reticulorumen
• Very important function for the ruminant
– Neutralizes 50% of VFA produced in R-R
• Saliva production positively correlated with
rumination chewing
– Diet effect due to composition and particle size
• Source of P for microbes to synthesize
nucleoproteins, phospholipids, and nucleotide
coenzymes
Source of buffers + nutrients &mode for waste excretion
– Route for disposal of urea and uric acid (these N
compounds are waste products from intermediary
metabolism and the body needs to deal with them)
• The presence of urea in saliva is one of the fates of
urea produced in liver
– What are the others?
• Urea used by rumen microorganisms as a source of
nonprotein N (can you define what NPN is ?):
ruminant can recycle NPN
• May be very important if cattle on low N diet
– When would this happen?
Protective role
– Mucus protects mucosa in oral cavity, esophaghus,
and abomasum
– Acts as an Antifoaming agent
– Provides aqueous media for solids that are not
compressed in the fibrous raft
• Amounts produced per day
• Humans: 1 to 2 liters per day
• Sheep: 16 liters per day
• Cattle: 60 to 200 liters per day
Pharynx
Short caudal continuation of oral cavity
leading into the esophagus
– Structure similar to monogastrics
– Involved in rumination and eructation
Esophagus
Connecting tube between pharynx and
reticulo-rumen
– Functions bi-directionally in ruminants
• Swallowing, Regurgitation (rumination)
Nonglandular region of simple stomach
(esophagheal region) expanded into 3 distinct
diverticula which make up the forestomach or
proventriculus
– Forestomach is nonsecretory and made up of
rumen, reticulum, and omasum
Glandular portion of the stomach
is the
abomasum which functions identically as the
simple stomach in monogastrics
Size (capacity) of cow stomach
42.5 to 54 gallons depending on source
• 67.5% of total GIT capacity
• Reticulo-rumen makes up 56.3% of total GIT
capacity
Reticulum:
most cranial part of forestomach
– Has honeycomb structure as mucosa arranged
into intersecting ridges
– Tends to accumulate wires and nails that are
consumed
• Can penetrate into pleural + pericardial spaces and
liver to cause Hardware Disease
• Producers will place magnet in reticulum to prevent
Hardware Disease
– Pumps liquid into rumen and regulates outflow of
digesta into rumen and omasum
– Has similar functions to rumen so together often
referred to as reticulorumen
Reticulorumen:
Large microbial fermentation vat where bacteria,
protozoa, and fungi ferment ingested feed and
produce endproducts which the “host” ruminant can
use as metabolic substrates
– Site of chemical digestion via microbial enzymes
– Presence of papillae in the ventral rumen to absorb the
products of microbial digestion (chemical digestion)
especially for VFA
• Finger-like structures (10 mm x 2 mm) covering the
rumen wall
– Increasing surface area available for absorbing
products of rumen fermentation
• Particularly well-developed in ventral portion of the
rumen
Involved with passage of nutrients
• Rumen also mechanically or physically digests
feedstuffs due to mixing actions
• Ingested food (ingesta) can only leave reticulorumen
if it reaches critical particle size (PS)
– Attains critical PS via physical and(or) chemical
digestion
– Ingesta then enters the omasum
Why Do We Call Them Ruminants?
• Process found in pseudo- and true ruminants
• Ruminate feedstuffs from 3 to 10 hours per day
depending on the particle size of feed consumed
– Chewing their cud
• Rumination includes regurgitation of previously
ingested feed (need for reverse peristalsis),
masticating or chewing feed again, adding more
saliva, and reswallowing: 4 R’s
– Regurgitation
– Remastication
– Reensalivation
– Reswallowing
Functions of Rumination
Rumination needed to attain critical particle size
for feed to leave the reticulorumen
– Rumination reduces particle size (physical digestion) +
provides more surface area for microbial digestion
(chemical digestion)
• May reduce digestibility but can increase DMI
• Increases density of ingesta
• Rumination increases saliva production 3 to 5
fold which is important to buffer VFA produced
in R-R
• Rumination increases mixing of digesta and
eructation
Omasum:
Spherical in shape: size of a basketball in cattle
• Entrance is the reticulo-omasal orifice
– 1 inch slit in cattle
• Sheets of muscular laminae (leaflike folds, plies,
sheets) which have small horny papillae to grind
the feed
• Also called Manyplies due to presence of the sheets
or leaves: 90 to 130 leaves in total
• Leaves cause dramatic increase in surface area
(SA)
• 1/3 of the SA in the stomach for cattle
• Minor site for microbial fermentation
Sorts feedstuffs so that larger size particles are
retained in reticulorumen
– Most particles found in the omasum < than 1 mm
• Major site of absorption for VFA, electrolytes
(especially Mg) and water
– Removes 60-70% of water from ingesta
• Helps regulate movement of digesta from
reticulum to the abomasum
• May have an important role in absorption
(including amino acids & glucose)?
Abomasum:
Ingesta passes from omasum into the abomasum
• True stomach in ruminants
– First glandular component in ruminant GIT
• Analogous to monogastric stomach
– Secretes HCl and pepsin: analogous to the
nonruminant stomach; initiates gastric digestion
• Functions also as an inflow stabilizer to the
duodenum
• Lysis of bacteria via the enzyme, lysozyme
• May be involved in reabsorption of H2O
Advantages of Pregastric Fermentation
• Can utilize fibrous diets (high in NDF) that
nonruminants would be unable to
– Enable utilization of cellulose (β- glucose linked
polymer) which is the most abundant CHO in plants
• Synthesize high biological value (BV) microbial
protein (MP), rich in essential amino acids
(E-AA) from low BV plant proteins (deficient in
E-AA), NPN (urea and uric acid), & recycled
nitrogenous end-products
– What is microbial protein? Should it be renamed
microbial nitrogen?
• Synthesize all B vitamins
• Ability to detoxify some poisonous
compounds
– Oxalates, cyanide, alkaloids
• More effective use of fermentation endproducts
including:
– Volatile fatty acids, microbial protein, B
vitamins
• Decrease in handling undigested residues
• In wild animals, it allows animals to eat and
run
Disadvantages of Pregastric Fermentation
• Need food at regular intervals • Need to spend long times chewing food (4 to 7 h/d) and ruminating (chewing cud): about 8 h /d • Releases large amounts of volatile acids into environment Need safeguards to ensure fermentation vat works – Large amounts of alkaline saliva production (Why?) – Regulates powerful mixing movements of the FS – Ability to get rid of gases produced from microbial fermentation (eructation) – Need for rumination – Need to attain critical PS to leave R-R via chewing from ingestion and rumination: 2 to 4 mm – Need intermediary pathways in the animal to use products of microbial fermentation What is a major one? • Fermentation is inefficient with energy losses – 5 to 8% from methane production – 5 to 6% from Heat of fermentation • Potential wasting of high quality proteins – Microbial N production includes nucleic acids which make up 25% of total microbial N • Inefficient production of ATP in the animal using VFA vs. absorbing glucose from s.i. • Ruminants are susceptible to ketosis • Ruminants are susceptible to toxins produced by rumen microbes – Nitrates converted in rumen to Nitrites – Urea converted in rumen to Ammonia – Nonstructural carbohydrates (α-glucosee linked polymers including starches & sugars) converted in rumen to Lactic acid
Esophagheal or Reticular Groove
Cardia of the esophaghus enters into a
space common to reticulum and rumen
• Mucosa here can form into 2 heavy
muscular folds that can form a groove or
tube which will connect the cardia of the
esophaghus to the omasum
• This tube or groove forms when a “baby”
ruminant nurses the dam
– Function of the “tube”; have milk bypass entry
to the reticulo-rumen so it won’t sour
• High quality milk shouldn’t be fermented or you
waste high quality nutrients found in milk
Small Intestine
Site where most digestion takes place in
monogastric or simple stomach animals and
90% of nutrient absorption
– Still very important for digestion and absorption in
ruminants
• Primary site for CHO, lipid, protein digestion
and absorption of vitamins, minerals, and
water
• 3 sections: duodenum, jejenum, ileum
• Pancreatic + hepatic bile ducts enter duodenum
to provide secretions to aid digestive process
3 sections: duodenum, jejenum, ileum
– Duodenum
• Begins at pylorus (abomasal-duodenal juncture)
• Pancreatic + hepatic bile ducts enter duodenum to
provide secretions to aid digestive process
– Jejunum
• Middle section
• Longest section, highly coiled
• Site for most digestion and absorption
– Ileum
• Final section (terminates at ileal-cecal juncture)
• Extensive mucus secretion
Enzymes Acting In the S.I.
Source: Pancreas
Trypsin, Chymotrypsin: endopeptidases that attacks
peptide linkages in interior of the protein
– Produce AA and peptides
• Carboxypeptidases: exopeptidase which splits off
terminal AA
• Alpha-amylase: converts starch to oligosaccharides
• Lipase: convert TG into FA and glycerol
• Ribonucleases to degrade RNA & DNA
Enzymes Acting In the S.I.
Source: Enterocyte
- Maltase: Oligosachharides to MS
- Sucrase: Oligosachharides to MS
- Lactase
- Enterokinase
- Amino- and di-peptidases
- Nucleosidases
Large Intestine
• Last part of GIT which includes
– Cecum: blind sac with microbial fermentation
– Colon with microbial fermentation
– Rectum: for fecal storage
– Anal canal with anus as the exterior opening
– No villi present here
• Functions of large intestine
– Microbial fermentation and vitamin synthesis
especially in cecum + colon
– Electrolyte and water absorption
– Fecal formation
– Expulsion of feces
Microbial fermentation in large intestine of most
mammals with production of:
–VFA: used for ?
– Proteins: are these valuable to the
animal?
– Vitamins?
• Which ones & are the quantities important?
Functions of the Large Intestine
• Fermentative digestion
– Bacteria similar to rumen, but no protozoa
– LI digestion may account for as much as:
• 27% of cellulose digestion
• 40% of hemicellulose digestion
• 10% of starch digestion
– Only important in conditions that increase the amount
of fermentative carbohydrate entering the LI
• Increased rate of passage of forages (How?)
• High grain diets
– May account for as much as 17% of total VFA
absorption
– VFAs are efficiently absorbed, but primarily used as
energy source for mucosa cells
• Absorption of ammonia-N
– May account for as much as 30 to 40% of the net
transport of N into body fluid
– Absorbed N may be used for:
• Synthesis of nonessential amino acids
• Recycling of N to the rumen
– Important on low protein diets
• Mineral absorption
– Na, K, Ca, P, Co, Mn, Mg, Cu, Zn, Cl
• Water absorption
– 90% of water entering the LI
• Capacity of the total GIT
–Horse: 66%
–Pig: 36%
–Cattle: 12.5% (56% of GIT is
reticulorumen)
Pancreas
• Endocrine function (produce hormones
which is released into the blood stream)
– Produces hormones, insulin and glucagon
for regulation of blood glucose
• Exocrine function (produce a substance
which is secreted out through a duct)
– Major digestive enzymes for carbohydrates,
lipids, proteins, nucleic acids
– Sodium bicarbonate to neutralize stomach
acids, stop action of pepsin, and increase pH
in small intestine: Why is this important?
– Pancreatic duct enters proximal duodenum
Liver
Largest gland in body (1 to 2% of BW); in contact with
diaphragm
• First organ or gland to process blood coming from GIT
via portal vein carry products of absorption
• Metabolic powerhouse of the body
– CHO metabolism
• Converts glucose to glycogen and TG (triglycerides)
• Breakdown glycogen into glucose
• Converts AA (amino acids), LA (lactic acid), and C3
(propionate) into glucose
• Metabolic powerhouse of the body
– Protein metabolism
• Deaminate AA for use in ATP synthesis
• Convert AA to CHO and fats
• Synthesize plasma proteins (albumin, prothrombin,
fibrinogen)
• Metabolic powerhouse of the body
– Lipid metabolism
• Hepatocytes can store TG
• Use FA to make ATP
• Synthesize Lipoproteins and cholesterol
• Cholesterol used to make bile salts
–Detoxification
•Detoxifies alcohol and AB
•Detoxify NH3, converting it to urea
–Synthesize bile salts which are used to emulsify lipids
in the s.i.
–Storage of fat soluble vitamins (A, D, E, and K) and
B12, Fe, Cu, and glycogen
• Metabolic powerhouse of the body
–Helps in the activation of active form of Vitamin D
•Converts cholcalciferol into 25
hydroxycholcalciferol
•Kidney converts 25 hydroxycholcalciferol into
1,25 dihydroxycholcalciferol which acts on intestinal
cells to increase Ca absorption
•Includes largest part of macrophage system with the
presence of Kupffer cells which remove foreign materials
that enter the blood from the stomach and intestines
– Kupffer cells also remove tissue debris such as old and
fragile RBC (erythrocytes).
Gall Bladder
• Found in all domestic animals except the
horse
• Used to store bile which is needed for fat
digestion
– Emulsifies lipids to enhance action of
pancreatic lipase
– Bile enters proximal duodenum via common
bile duct near where pancreatic duct enters
Kidneys
• Excrete metabolic byproducts/toxins
• Reabsorption
– Urea, etc.
• Acid/Base balance
Overview of Nutrient Digestion
& Metabolism
• Ingestion • Ruminal Fermentation – VFA absorption – Microbial protein synthesis • Intestinal digestion – Nutrient absorption – Fecal excretion • Liver Metabolism • Incorporation into tissue • Urinary excretion
Requirements for the rumen
- constant supply of nutrients
- water
- continuous removal of products of digestion/fermentation (gases, VFA’s, NH3
- Regulation of PH to prevent acidosis (problems if this doesn’t occur)
Rumen Provides Environment Ideal
for Anaerobic Fermentation
Substrate availability/Ruminal Volume – Feed fermented to volatile fatty acids “VFA” – Passage and absorption – no build-up of non-digestible substrate for the most part – Microbial biomass produced • Temperature – 38 - 42C • Regulated pH – Saliva – VFA absorption (passive) • Oxygen limiting – Anaerobic; does this mean there is no O2 in the rumen?
Ruminal Microbe Population
• Symbiotic relationship – With each other – With the host • Bacteria – 109 – 1012/g – > 200 species – Can be strict anaerobes or facultative anaerobes • Protozoa – 103 – 106/g • Anaerobic Fungi
Rumen Bacteria
• Major contributor to microbial fermentation
– One of major focuses in ration fermentation for high and
low producing animals is to ensure the nutrient
requirements of the microbes are met
• Most dynamic population with large diversity
of species and activities
• Symbiotic relationship with each other
– Crossfeeding
– Cellulolytic bacteria (fiber digesters) outnumbered by noncellulolytic
(digest starch & sugars) yet the latter benefit
from the actions of the cellulolytics
• Most extensively studied, yet much yet to learn
Classification of Bacteria
• Fibrolytic
– Cellulolytic
• Cellulose
– Hemicellulytic
• Hemicellulose (HC)
– What is the difference between cellulose & HC?
• Cellulose made up of β 1-4 glucose linked polymer
• Hemicellulose is a heterogenous collection of
polysaccharides which can be β 1-2, 1-3, and 1-4 linked
polymers
– Xylan
– Arabinose
– Uronic acid
• Hemicellulose more closely bound to lignin than cellulose
Lignin
• Not a CHO but a polyphenolic compound
• Protects the plant
– Chemical + biological (disease) resistance
– Provides mechanical strength
• Only binds to hemicellulose
• Found in stems rather than in leaves
• Concentration in plants influenced by:
• Maturity
• Ambient temp: Hi temps increases lignin
synthesis
Major factor limiting digestion of forage cell
walls
• Physically encrusts fiber
• Protects cell wall CHO from attack
• Alters stereochemistry of plant CHO
• May be toxic to specific cellulolytic bacteria
• Which chemical analysis or analyses will we find
lignin?
Fibre Digesters
• Fibrobacter succinogenes: Most common cellulolytic bacterium • Butyrivibrio fibrisolvens • Ruminococcus albus • Ruminococcus flavefaciens • Prevotella ruminicola – Digests plant cell wall polysaccharides (ie. xylans and pectins) but not cellulose • Succinivibrio dextrinosolvens: Ferments hemicellulose and pectin • Ruminococcus sp. – Degrade fibre – Colonize plant tissues
Methanogens
• Keep CO2 and hydrogen low • Interspecies hydrogen transfer • Produce methane • Compete with acetogens (use CO2 for acetate production) • Target of extensive research: Why ? • Methanogens – Methanobacterium formicicum – Metanobrevibacter ruminantium – ETC
Starch digesters
• Butyrivibrio fibrisolvens
• Streptococcus bovis: capable of rapid growth
– Plays role in lactic acidosis development
• Ruminobacter amylophilus: usually in low
numbers but is a major starch digester
• Prevotella ruminicola: makes up 60% of
total rumen bacteria
• Selenomonas ruminantium: found in high
numbers on cereal grains
• ETC!!!
• Sugar Utilizers
– Lactobacillus: ferments sugars to produce lactate • Role in lactic acidosis – Prevotella ruminicola – Butyrivibrio fibrisolvens – ETC • Acid Utilizers – Selenomonas ruminanium – Veillonella alcalenscens – Megasphaera elsdenii – ETC
Acid utilizers
– Selenomonas ruminanium
– Veillonella alcalenscens
– Megasphaera elsdenii
– ETC
Protein Digesters
- Butyrivibrio fibrisolvens
- Prevotella ruminicola
- Ruminobacter amylophilus
- Selenomonas ruminantium
- ETC!!!
Protozoa
• Anaerobic, Approximately 104/ml • Much lower numbers than rumen bacteria • Vary considerably with feed type • May contribute up to 40% of ruminal microbial N • Role in Soluble CHO fermentation • Engulfment and digestion of bacteria – Two groups: • Entodiniomorphids • Vestibuliferids
Entodiniomorphids
Engulf particles or other protozoa/bacteria
Digest starch, cellulose, hemicellulose
Entodinium
Epidinium
Ophryoscolex
Polyplastron
Vestibuliferids
• Approximately 20% of protozoa in rumen • Numbers increase before feeding • Non-structural polysaccharide and soluble sugar digestion • Colonize plant tissue • Consume bacteria • Isotricha • Dasytricha
Fungi
• Neoallimastix, Caecomyces, Pyromyces, Orpinomyces, Anaeromyces • <8% of total microbial mass • Access and colonize plant tissue • Greater with increased fibre, longer forages • Cellulolytic activity • May contribute up to 30-40% of ruminal fibre digestion • Certain species can digest lignin • Proteolytic
Starch vs. Cellulose
Alpha glucose linked polymer: animal enzymes can
digest if it is available to the animal enzyme
Beta glucose linked polymer: digested by microbial
fermentation
In lectures, often will refer to alpha-linked and betalinked
glucose polymers
Partitioning With Neutral Detergent
Solution (NDF Analysis)
• NDR or NDF: Hemicellulose Cellulose Lignin Some Protein Bound N Minerals Cuticle Hemicellulose and Cellulose are beta glucose linked polymers • ND Solubles = Cell contents Sugars Starch Lipids Fructans Pectin Beta Glucans Proteins Which of the CHO here are alpha vs. beta linked polymers?
Partitioning With Neutral Detergent
Solution (NDF Analysis)
• 100 - %NDF in feed = Cell contents Cell contents fraction will be completely available to microorganisms (pregastric and hindgut) Cell contents less pectin and beta glucans will be completely available to animal enzymes
Carb degredation
• Fibre (definition can be vague)
– High in forages or roughages (hay, pasture, silage)
– Not digested by mammalian enzymes
– Cell wall components or structural CHO in plants
– NDF, ADF
• Hemicellulose
• Cellulose
• Lignin (mostly not digested)
– What about soluble fibres? What do they include?
• Pectin: rich in galacturonic acid
– α 1-4 linked polymers
– Fermented and not digested by animal enzymes
• β glucans
– β 1-3 and β 1-4 linkages
– Fermented and not digested by animal
enzymes
• Sugars
– In byproducts such as molasses
• Starch
– High in grains: grain to grain variation;
relate the amount of starch to which nutrient
value?
• 47% to 95% digested in R-R
• Action of alpha-amylases (extracellular
enzyme)
– Found in cell-free rumen fluid but 70% associated with
particulate-bound microorganisms
• Both bacteria and protozoa will engulf
CHO and contain storage polysaccharide
Cellulose Digestion
• Approximately 90% occurs in R-R
• 2 step process
– Microbial attachment
– Hydrolysis
• Lag period (delay) in digestion as:
– Substrate must be exposed: how does that happen?
– Bacteria must get to the fiber (slow process)
– Feed particle must be wet (in 3120, how did you
prep your bags before incubation?)
– Bacteria must attach to the fiber
– Bacteria need to use extracellular enzymes
Effective NDF
• The fraction of the feed that stimulates
chewing activity
• Chemical & Physical characteristics
• Particle size
• Effect on rumen pH & fiber digestion
• Feed composition guides will often state
the eNDF content
VFA Production in Rumen
• Why do rumen microbes make volatile fatty
acids (VFA)?
– Anaerobic pathways to provide ATP for microbes
• Sometimes called Short Chain Fatty Acid
(SCFA)
– 2 – 5 Carbons in length
• Acetate, Propionate, Butyrate, Isobutyrate,
Valerate, Isovalerate
– Absorbed in rumen and anywhere else?
– Metabolized, used as energy source, precursor for
other molecules, signal for metabolic activity?, tissue
health
– 50-85% of metabolizable energy comes from VFA
• Forage diet
Acetic acid
2 carbons
Propionic acids
3 carbons
