Lecture 9 - Fatty Acid Metabolism

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Isfahan University of Technology Isfahan, Iran
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The ruminant digestive tract

• The wall of digestive tract as a hollow organ
  consisting of several layers
• Mucosa
• Submucosa
• Muscularis externa
• Serosa/adventitia

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The ruminant digestive tract

• The functions of mucosa
• Secretion of enzymes, acid, mucin, hormones and
  antibodies.
• Absorption of the break down products of
  digestion, water, vitamins and etc.
• Barrier to prevent the entry of antigens,
  pathogenic organisms, and immunologic protection.

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The ruminant digestive tract
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The ruminant digestive tract
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The ruminant digestive tract
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Esophagus

• The properties of esophagus
• It is the least complex section of the digestive
  tube.
• Its role in digestion is simple
• To convey boluses of food from the pharynx to the
  stomach.
• Absorption in the esophagus is virtually nil.

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Esophagus

• The mucosa does contain a few mucous glands.
• The architecture is that of a typical hollow
  organ with four layers.
• The lamina propria contains a relatively dense
  connective tissue, with the elastic fibers.

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• Many seromucous glands are present in the
  submucosa.
• In ruminants, glands are present in the cranial
  third of the esophagus.
• Submucosal plexus (Meissners) are present but
  may be quite small.

Esophagus
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Esophagus

• The musculature may be
• Skeletal muscle
• Smooth muscle
• A mixture of smooth and skeletal muscles

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Esophagus

• Contraction of the muscle cells (peristalsis)
  help to propel the boluses of ingesta toward the
  stomach.

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The ruminant stomach and its development
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The ruminant stomach and its development

• The wall of stomach is made of 4 layers
• T. Mucosa
• T. Submucosa
• T. Mascularis
• T. Serosa

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The ruminant stomach and its development
Solid lines internal oblique fiber (ruminal
pillars, lips of reticular groove, omasal
pillar) broken lines longituidal fibers wave
lines circular fibers. At any given place, there
are only two muscle layers in the stomach wall.
1 cardia 2 reticulum 3 rumen 4 omasum 5
abomasum.
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The ruminant stomach and its development

• Preruminant stomach and food digestion
• The calf is a monogastric (birth to 2 weeks of
  age).
• The abomasums is actively involved in digestion.
• Readily fermentable carbohydrates are important
  for the rumen development.

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Size of ruminant stomach compartment
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Pre-ruminant period
Coming from esophagus
Leading to omasum
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Size of ruminant stomach compartment
-

-
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Transition from pre-ruminant to ruminant
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Transition from pre-ruminant to ruminant

• Absorptive surface area is enhanced by
  increasing
• Papillae length
• Papillae width
• Papillae density

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Transition from pre-ruminant to ruminant

• Two important factors for stimulating papillae
  growth
• Presence and absorption of volatile fatty acids
  (VFAs) in rumen
• Stimulatory effect of different VFAs is not
  equal
• Rumen epithelial ketogenesis (BHBA production)

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Transition from pre-ruminant to ruminant
A caudal portion of the caudal ventral blind
sac RB right side and LB left side caudal
dorsal sac RC right side and LC left side
cranial dorsal sac RD right side and LD left
side cranial ventral sac and RE right side and
LE left side ventral portion of caudal ventral
blind sac (Lesmeister et al. (2004)
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Transition from pre-ruminant to ruminant
Undeveloped Rumen
Developed Rumen
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Transition from pre-ruminant to ruminant
Importance of diet to rumen development (6 weeks
of age)
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Transition from pre-ruminant to ruminant
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Transition from pre-ruminant to ruminant

• Five factors affect the rumen development
• Establishment of bacteria in the rumen
• Liquid in the rumen
• Outflow of material from the rumen
• Absorptive ability of the tissue
• Substrate available in the rumen.

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Establishment of bacteria in the rumen

• At birth day the rumen is sterile
• Aerobic bacteria
• Change of bacteria population

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Establishment of bacteria in the rumen

• Prolonged milk feeding may retard
• Typical ruminal microflora
• Establishment of protozoa

• Feeding DM affect type of rumen bacteria
• Decreasing aerobic bacteria
• Increasing anaerobic bacteria

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Liquids in the rumen

• Milk does not help rumen development at all
• Water is essential for rumen development
• Without sufficient water, bacteria cannot grow,
  and ruminal development is slowed.

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Outflow of material from the rumen

• Measures of ruminal activity
• Rumen contractions
• Rumen pressure
• Regurgitation (cud chewing)
• Little muscular activity at birth.

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Outflow of material from the rumen

• Effect of chemical composition of concentrates
• A shift in the microbial population
• Increasing butyrate and propionate production at
  the expense of acetate.

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Outflow of material from the rumen

• Forages, have an increased ability to maintain a
  higher ruminal pH, due to
• A larger particle size
• An increased fiber content

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Outflow of material from the rumen
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Absorptive ability of the rumen tissue

• The end-products of fermentation.
• Butyrate and propionate most readily absorbed by
  rumen epithelium.

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Availability of substrate

• The primary factor determining ruminal
  development is dry feed intake.
• Starter
• Proper stimulation for rumen development

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Changes in rumen muscularization

• Feed physical structure
• Development of rumen muscularization
• Development of rumen volume
• Stimulation of rumen motility

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Physiology and ontogeny of rumen development

• Two important aspects for development of rumen
• Ruminal growth and cellular differentiation
• A major shift in the pattern of nutrients being
  delivered to the intestine and liver
• Thus nutrient delivered to peripheral tissues

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Control of ruminal epithelial cell proliferation

• In vivo and in vitro studies using mitotic
  indices for ruminal epithelial cell
  proliferation.
• Butyrate may induce a mitotic proliferation
• Propionate and acetate have been shown to
  stimulate mitotic indices

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Control of ruminal epithelial cell proliferation

• Contradiction in response to VFAs by in vivo and
  in vitro.
• The differences may be attributed to indirect
  pathways during in vivo condition.

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Control of ruminal epithelial cell proliferation

• Some hormones and growth factors may have
  mediator effect
• Insulin, Pentagastrin, Glucagon
• IGF-1, EGF
• Cortisol

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Neonatal ruminal epithelial metabolism

• Primary source of energetic substrates in
  neonatal ruminant
• Intestinally absorbed nutrients

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Neonatal ruminal epithelial metabolism

• The neonate and mature ruminants patterns for
  cellular bioenergetic
• Effect of glucose in neonatal rumen
• Effect of butyrate and lactate

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Liver metabolism rumen development

• The liver undergoes a maturation process of its
  own in response to ruminal development
• The most notable of changes is the shift from a
  glycolytic to glucogenic liver.

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Liver metabolism rumen development

• Liver adaptation in the developing animals
• Shift from primarily intestinally absorbed
  glucose, long-chain fatty acids, and milk-derived
  amino acids to SCFA, ketones, amino acids from
  feed and microbial sources, and other dietary
  compounds.

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Liver metabolism rumen development

• A basic reduction in enzyme capacity for
  hepatic glucose oxidation via glycolytic and
  hexose monophosphate pathways
• Glucose-6- phosphate dehydrogenase
• 6-phosphogluconate dehydrogenase
• Fructose 1,6-bisphosphate aldolase
• Glyceraldehyde 3- phosphate dehydrogenase

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Liver metabolism rumen development

• A rapid increase in activity of hepatic
  gluconeogenic enzymes
• Glucose 6-phosphatase activity having been shown
  to double during this period

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Rumen parakeratosis

• Parakeratosis have some adverse effects
• Creating a physical barrier.
• Restricting absorptive surface area and volatile
  fatty acid absorption.
• Reducing epithelial blood flow and rumen
  motility
• Causing papillae degeneration and sloughing in
  extreme cases.

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Rumen parakeratosis

• Initial evidence of parakeratosis is papillae
  clumping and branching.
• Followed by papillae degeneration and sloughing.

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Rumen parakeratosis

• Concentrate diets
• Increased volatile fatty acid production
• Decreased rumen buffering capacity
• Subsequently decreased rumen pH

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Rumen parakeratosis

• Increased feed particle size
• Maintains epithelial and papillae integrity and
  absorptive ability.
• Increased rumination and rumen motility
• Increased salivary flow and buffering capacity
• Development of mature rumen function and
  environment.

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Bloat in young ruminant animals

• Bloat can affect either
• Abomasum
• Rumen
• Abomasal bloat is often rapidly progressive and
  life threatening.

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Bloat in young ruminant animals

• Factors contributing to abomasal bloat
• Overfeeding milk
• Feeding milk too fast
• Pathogens, such as Clostridium

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Bloat in young ruminant animals

• Clostridium perfringens types A, B, C
• Clostridia are normally found in the intestine
  of cattle and can survive for months in the soil.

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Bloat in young ruminant animals

• Overeating or abrupt diet changes tend to
• Produce indigestion that slows gut movement
• Providing the sugars, proteins and lack of
  oxygen needed for rapid growth of Clostridia
• Wet conditions also seem to favor this organism

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Bloat in young ruminant animals

• The other factors
• Impaction of the abomasum or intestines with
  non-feed substances such as bedding or hairballs
• Structural or physiological problems with the
  abomasum

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Bloat in young ruminant animals

• Management practices to consider include
• Colostrum management
• Feeding time
• Milk temperature
• Feeding equipment
• Antibiotics
• Feed ingredients
• Stress
• Health status