Transcript Lecture 9 - Fatty Acid Metabolism

Isfahan University of Technology
Isfahan, Iran
Advanced
Digestive Physiology
(part 2)
By: A. Riasi
(PhD in Animal Nutrition & Physiology)
http://riasi.iut.ac.ir
Mastication
 Teeth in ruminants
Mastication
 Chewing
of food is fast and irregular with
variable amplitude.
 During rumination the cud is chewed with:
• Much more slowly and evenly
• Usually on one side
• Occasionally changed to the opposite side
Mastication
 Direct and indirect effects of mastication:
• Break the stem and leaf fragments of food and to cud
solids into small particles.
• Movements of the teeth excite sensory buccal
mechanoreceptors.
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.
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.
Esophagus
• Many seromucous glands are present in the
submucosa.
• In ruminants, glands are present in the cranial third
of the esophagus.
• Submucosal plexus (Meissner’s) are present but
may be quite small.
Esophagus
• The musculature may be:

Skeletal muscle

Smooth muscle

A mixture of smooth and skeletal muscles
Esophagus
Contraction of the muscle cells (peristalsis) help to propel the boluses of ingesta toward the stomach.
The ruminant stomach and its development
The ruminant stomach and its development

The wall of stomach is made of 4 layers:
• T. Mucosa
• T. Submucosa
• T. Mascularis
• T. Serosa
The ruminant stomach and its development
The ruminant stomach and its development
1
3
4
2
5
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.
The ruminant stomach and its development
 Preruminant stomach and food digestion
From birth to about 2 weeks of age, the calf is a
monogastric.
The abomasums is the only stomach compartment
actively involved in digestion.
Readily fermentable carbohydrates are important for
the rumen development.
Size of ruminant stomach compartment
Size of ruminant stomach compartment
Size of ruminant stomach compartment
Pre-ruminant period
Pre-ruminant period
Coming from
esophagus
Leading to
omasum
Size of ruminant stomach compartment
Transition from pre-ruminant to ruminant
Transition from pre-ruminant to ruminant
 Absorptive surface area is enhanced by
increasing:
• Papillae length
• Papillae width
• Papillae density
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)
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)
Transition from pre-ruminant to ruminant
Undeveloped Rumen
Developed Rumen
Transition from pre-ruminant to ruminant
Milk only
Milk and grain
Milk and hay
Importance of diet to rumen development (6 weeks of age)
Transition from pre-ruminant to ruminant
Milk, hay and grain
Milk and hay
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.
Establishment of bacteria in the rumen
 At birth day the rumen is sterile
• Aerobic bacteria
• Change of bacteria population
Establishment of bacteria in the rumen
 Prolonged milk feeding may retard:
• Typical ruminal microflora
• Establishment of protozoa
Establishment of bacteria in the rumen
 Factors may affect calf’s rumen microflora
• Feeds
• Environment
• Bedding
• Hair
Establishment of bacteria in the rumen
 The numbers of total bacteria
 Change in types of bacteria by feeding
DM:
• Decreasing aerobic bacteria
• Increasing anaerobic bacteria
Establishing a rumen microflora
Establishment of bacteria in the rumen
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.
Outflow of material from the rumen
 Measures of ruminal activity:
• Rumen contractions
• Rumen pressure
• Regurgitation (cud chewing)
 Little muscular activity at birth.
Outflow of material from the rumen
 Solid feed intake stimulates:
• Rumen microbial proliferation
• Production of microbial end products
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.
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
Outflow of material from the rumen
1393 ،‫برگرفته از میرزایی و همکاران‬
Absorptive ability of the rumen tissue
 The rumen wall consists of two layers:
• The epithelial
• The muscular
Absorptive ability of the rumen tissue
 The end-products of fermentation.
 Butyrate
and
propionate
absorbed by rumen epithelium.
most
readily
Availability of substrate
 The primary factor determining ruminal
development is dry feed intake.
• Starter
• Proper stimulation for rumen development
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.
Rumen parakeratosis
 Initial evidence of parakeratosis is papillae
clumping and branching.
• Followed
sloughing.
by
papillae
degeneration
and
Rumen parakeratosis
 Concentrate diets:
• Increased volatile fatty acid production
• Decreased rumen buffering capacity
• Subsequently decreased rumen pH
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.
Changes in rumen muscularization
 Feed physical structure:
• Development of rumen muscularization
• Development of rumen volume
• Stimulation of rumen motility
Changes in rumen muscularization
 Understanding
the cellular biology and
physiological changes of rumen development:
• Neonatal calf digestion kinetics
• Development
of
low-impact
or
non-invasive
research procedures could be instrumental in
advancing this area further.
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
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
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.
Control of ruminal epithelial cell proliferation
 Some hormones and growth factors may
have mediator effect:
• Insulin, Pentagastrin, Glucagon
• IGF-1, Epidermal growth factor
• Cortisol
Neonatal ruminal epithelial metabolism
 In neonatal ruminant primary source of
energetic substrates are blood borne, derived
from intestinally absorbed nutrients.
 Difference between neonate and mature
ruminant for uptake of oxidizable substrates
by ruminal cells
Neonatal ruminal epithelial metabolism
 Ontogenic control of some of the critical
development changes of rumen:
• Increase in gene transcripts for 3-hydroxy-3methylglutaryyl-CoA synthase.
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.
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.
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
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
Bloat in young ruminant animals
 Bloat can affect either:
• Abomasum
• Rumen
 Abomasal bloat is often rapidly progressive
and life threatening.
Bloat in young ruminant animals
 Factors contributing to abomasal bloat:
• Overfeeding milk
• Feeding milk too fast
• Pathogens, such as Clostridium
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.
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
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
Bloat in young ruminant animals
 Management practices to consider include:
•
•
•
•
•
•
•
•
Colostrum management
Feeding time
Milk temperature
Feeding equipment
Antibiotics
Feed ingredients
Stress
Health status