Title: Lecture 9 - Fatty Acid Metabolism
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2Isfahan University of Technology Isfahan, Iran
3Rumen and reticulum properties
- The ruminoreticular fold partially separates the
reticulum and cranial sac of the rumen. - Pillars divide the rumen to dorsal and ventral
parts.
4- The dorsal part of rumen is divided to
- Cranial sac
- Dorsal sac
- Caudodorsal blind sac
- The ventral part of the rumen is divided to
- The ventral sac
- The caudoventral blind sac
Rumen and reticulum properties
5Ruminoreticular wall structure
- Highly vascularized connective tissue core is in
the mucosal layer of the finger-like papillae - Epithelium is involved in the absorption of
short-chain fatty acids.
6- In the reticulum the mucosal layer contains
laminae. - Conical projections (papillae) are found on the
surface of laminae. - The stratified squamous epithelium of reticulum
also absorb short-chain fatty acids.
Ruminoreticular wall structure
7Ruminoreticular wall structure
- The reticulum has a role in mechanical digestion
of food. - Myenteric plexus can be found between the
muscularis externa layers.
8Blood circulation of forestomachs
- Celiac artery supply the blood flow to
forestomach and the most part of abomasum. - The venous blood drains into the hepatic portal
vein.
9Innervations and the receptors
- The innervations of fore stomachs
- Vagal nerves (101 afferent/efferent ratio)
- Splanchnic nerves (31 afferent/efferent ratio)
10Innervations and the receptors
- The vagal nerves transmit sensory information
from two known kinds of sensory receptors - Tension receptors
- Epithelial/mucosal receptors
11Innervations and the receptors
- The splanchnic nerves transmit sensory
information from - Serosal receptors
- Possibly tension receptors
12- The movements serve to
- Mix the ingesta
- Aid in eructation of gas
- Propel fluid and fermented foodstuffs into the
omasum. - A cycle of contractions occurs 1 to 3 times per
minute.
Ruminoreticular motilities
13Ruminoreticular motilities
- Two types of contractions are identified
- Primary contractions
- Secondary contractions
14Ruminoreticular motilities
- Typical primary cycle consist of
- Biphasic (double) contraction of the reticulum
- Caudally moving monophasic contraction of the
dorsal ruminal sac - A contraction of the ventral ruminal sac
15- Secondary cycle may occur and consist of
sequential contractions of - The caudoventral ruminal blind sac
- A cranially moving contraction of the
caudodorsal ruminal blind sac followed by the
middorsal ruminal sac - A contraction of the ventral sac.
Ruminoreticular motilities
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17Ruminoreticular motilities
- When ingesta enter the foestomach, heavy objects
fall into the reticulum and lighter material
enters the rumen. - Added to this mixture are voluminous quantities
of gas produced during fermentation.
18Ruminoreticular motilities
19Ruminoreticular motilities
- The forestomachs possess a rich enteric nervous
system. - Contractions coordination need the central
input. - Motility centers in the brainstem control both
the rate and strength of contraction via vagal
efferents.
20Ruminoreticular motilities
- There are also vagal afferents from the rumen to
the motility centers which allow stretch
receptors and chemoreceptors in the rumen to
modulate contractility.
21Ruminoreticular motilities
- Feeble intrinsic contractions responsible for
the smooth muscle tone in the forestomach wall
arise from nervous activity in its intrinsic
nerve networks.
22Ruminoreticular motilities
- The gastric centers do not have spontaneous
activity and need to be driven by - Excitatory inputs
- Inhibitory inputs
23Ruminoreticular motilities
- The principal inputs to the gastric centers are
from - Forestomachs
- Abomasum
- Duodenum by way of vagus nerves
24Stimulus
Effect
Projections
Receptors
25Stimulus
Effect
Projections
Receptors
26Stimulus
Effect
Projections
Receptors
27- The known sensory receptor mechanisms are
responsible for the vagal inputs. - The tension receptors are located in the muscle
layer of different parts. - The epithelial receptors are located closed to
the basement membrane of the luminal epithelium
of the forestomachs.
Ruminoreticular motilities
28- Conditions inside the rumen can significantly
affect motility. - Acidic ruminal contents
- High roughage diet
Ruminoreticular motilities
29- Ruminants are well known for "cud chewing
- It provides effective mechanical breakdown of
roughage and increases substrate surface area. - Rumination is a unique characteristic of
- True ruminants (deer, giraffes, and bovidae)
- Pseudoruminants (camels and llamas).
Rumination and its components
30Rumination and its components
- Rumination occurs in resting.
- The highest incidences of rumination occur during
afternoon and middle of the night. - Many lactating ruminants ruminate while they are
suckling their young or are being milked.
31Rumination and its components
- The time spent ruminating by a given animal
depends on - The texture of the food
- The amount of food ingested
- Cattle may ruminate from 35 to 80 minutes per
kilogram of roughage consumed.
32Rumination and its components
- Pharmacological agents have been used to examine
the physiological mechanisms involved in evoking
rumination. - Volatile fatty acids
- Catecholamines
- Gastric hormones
- Opioids
- Autacoids
33Rumination and its components
- Rumination is centrally mediated by the "gastric
centers located at - Medulla oblongata
- Ventral hypothalamic area
- Tactile stimulation of the reticular and ruminal
epithelia is a powerful stimulus for rumination.
34Rumination and its components
- Sensory information from digesta that is
perceived in pillars - Digesta texture
- Digesta consistency
- Rumen fill
35Rumination and its components
36Rumination and its components
- Four phases of a rumination cycle
- Regurgitation
- Remastication
- Reinsalivation
- Reswallowing
- Regurgitation starts with an inspiration effort.
37Rumination and its components
- The bolus is carried into the mouth by reverse
peristalsis. - Antiperistaltic waves of regurgitation passes
over the esophagus at a velocity of 0.2 m per
second.
38Rumination and its components
- In about two seconds, the "retained" bolus has
the fluid squeezed out of it. - This fluid is immediately swallowed, and the
remainder is chewed, reinsalivated, and
subsequently swallowed.
39Rumination and its components
- Slower and more regular rate in remastication
phase
40Rumination and its components
41Rumination and its components
- The rate and duration of rumination chewing are
controlled - The texture (coarseness)
- Quantity of the food
42Rumination and its components
- The reinsalivation phase of rumination coincides
with the remastication phase. - Rumination saliva and ingestion saliva are
secreted at about the same rate and about 2.5
times the resting rate.
43Eructation
- Eructation is the physiological process of
expelling ruminoreticular gases - Carbon dioxide, 65
- Methan, 25
- Nitrogen, 7
- Oxygen, 0.5
- Hydrogen, 0.2
- Hydrogen sulfide, 0.01.
44Eructation
- The eructation is associated with almost every
secondary ruminal contraction. - Eructated gas travels up the esophagus at 160 to
225 cm per second - Interestingly, a majority is actually first
inspired into the lungs, then expired.
45Eructation
- A large portion of the eructated gases is
inspired and recycled into the organism by
absorption into the lungs.
46Eructation
- The rumen raft is the site of origin of most of
the gases of fermentation. - When dorsal surface of raft splits, releasing of
free gas into the gas layer occur. - Not much of the gas is absorbed, and most must
be eliminated by eructation.
47Eructation
- If the gas layer reaches the cardia and clear it
of fluid, the eructation mechanism is evoked. - Eructation is a vagovagal reflex, with centers
in the medulla ablongata. - Mechanical receptors to detect distention are
present in - Rumen dorsal sac
- Reticular groove
- Around the cardia and esophagus
48Eructation
- The primary type of rumen contraction always
follows the biphasic reticular contraction and
spread caudally. - In cattle
- 66 with the secondary type of rumen
contraction, - 20 with the primary type.
49Eructation
- In sheep
- 3 no dependent rumen motility
- 37 with secondary-type rumen contractions
- 60 with the time with the primary type
50Strategies for lower methane emission
- Increasing the efficiency in which animals use
nutrients to produce milk or meat. - Rumen modifiers such as ionophores improve dry
matter intake efficiency and suppress acetate
production, which results in reducing the amount
of hydrogen released.
51Strategies for lower methane emission
- The grinding and pelleting of forages can reduce
emissions by 40 . - Dietary fats have the potential to reduce CH4 up
to 37.