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Anatomy of the Anatomy of the Ruminant StomachRuminant Stomach
• Extensive pre-gastric Extensive pre-gastric microbial fermentationmicrobial fermentation
• 4 compartments 4 compartments
Cow rumen
Cow reticulum
The inside of the omasum
Reticular epithelium
The interior surface of the rumen
Lining or epethelia Lining or epethelia of the reticulo-of the reticulo-
rumenrumen
cattle (left), sheep cattle (left), sheep (right)(right)
• Papillae most dense in Papillae most dense in the ventral sacthe ventral sac
• where most absorption where most absorption occursoccurs
Papillae Papillae developmentdevelopment
Fermentation/absorption driving factor
Reticular Reticular groove groove (pinned (pinned
in an open in an open position)position)
cardiacardia
reticuloreticulo-omasal -omasal orificeorifice
Reticular Reticular groove groove (in a (in a
closed closed position)position)
esophaguesophaguss
reticularreticular
groovegroove
OmasumOmasum
tightly packed with tightly packed with digesta (left)digesta (left)leaves or foldsleaves or folds
Cow omasum
Function of the Function of the OmasumOmasum
• acts as a filter to sort out acts as a filter to sort out liquid and particles for liquid and particles for passage to the abomasumpassage to the abomasum
• selective retention of the selective retention of the coarse particlescoarse particles
• absortive site for water, absortive site for water, VFA, Na, K, etcVFA, Na, K, etc
• reduction of the net reduction of the net volume entering the volume entering the abomasumabomasum
AbomasumAbomasum
fundic fundic folds folds (unique)(unique)
duodenumduodenum
pylorupyloruss
fundifundicc
Cow abomasum
Function of the Function of the AbomasumAbomasum
• digesta to abomasum digesta to abomasum continuouscontinuous
• thus, continuous secretion thus, continuous secretion of gastric juice (pepsin. of gastric juice (pepsin. HCl)HCl)
• stimulated by VFA and stimulated by VFA and lactic acidlactic acid
• short retention time (< 3 short retention time (< 3 h)h)
• digesta entering: pH 6.0digesta entering: pH 6.0• digesta leaving: pH 2-3digesta leaving: pH 2-3
MotilityMotility
• Mixing of digestaMixing of digesta• passage of digesta passage of digesta
through the reticular-through the reticular-omasal orificeomasal orifice
Rumen motilityRumen motility
• Contraction/relaxation of Contraction/relaxation of reticulo-rumenreticulo-rumen– moves and mixes digestamoves and mixes digesta– passage of digesta through the passage of digesta through the
reticular-omasal orificereticular-omasal orifice
• initial contraction of the initial contraction of the reticulumreticulum
• 2nd powerful contraction of 2nd powerful contraction of reticulumreticulum
• wave of contractions passing wave of contractions passing over rumenover rumen
• about 60 secsabout 60 secs
Contraction Contraction sequence sequence of RRof RR
Movement of Movement of DigestaDigesta
RuminationRumination
- “cud-chewing”- “cud-chewing”
- regurgitation of digesta- regurgitation of digesta
- re-swallowing of liquid - re-swallowing of liquid and fine particlesand fine particles
- mastication/ensalivation - mastication/ensalivation of bolus (40 - 70 sec)of bolus (40 - 70 sec)
- pause (2 - 6 sec)- pause (2 - 6 sec)
Eating and Eating and ruminatingruminating
• increases saliva secretionincreases saliva secretion• helps reduce particle size helps reduce particle size
of feedof feed• promotes passage of promotes passage of
digesta from the RR digesta from the RR which alleviates gut fillwhich alleviates gut fill
EructationEructationc.c. Rumen contraction forces gas Rumen contraction forces gas
to the back and then forwardto the back and then forward
d.d. Gas forced up esophagus to Gas forced up esophagus to the tracheathe trachea
GAS GAS
GAS
Esophageal Esophageal FistulaeFistulae
Rumination Rumination boluses (liquid)boluses (liquid)
upup downdown
Rumination Rumination boluses (dry)boluses (dry)
upup downdown
Role of Role of ruminationrumination
• saliva saliva secretion secretion – 2-4 x higher 2-4 x higher
than during than during restingresting
• particle size particle size reductionreduction
Chewing activity of dairy Chewing activity of dairy cowscows
00
22
44
66
88
1010
1010 1515 2020 2525 3030 3535 4040
NDF-f (% DMI)NDF-f (% DMI)
EatingEating RuminatingRuminating
alfalfa hayalfalfa hay
alfalfa hayalfalfa hay
orchardgrassorchardgrass
corn silagecorn silage
1010 1515 2020 2525 3030 3535 4040
h/d
h/d
Ruminating, h/dRuminating, h/d
Total chewing, h/dTotal chewing, h/d
Diets contained 5% forage (DM basis)Diets contained 5% forage (DM basis)Ruminating, h/dRuminating, h/d 4.4 4.4 5.55.5
Total chewing, h/dTotal chewing, h/d 7.3 7.3 7.97.9
9.49.4
16.116.1
CoarseCoarse 8686
MediumMedium 8181
MediumMediumfine fine 7575
FineFine 6969
Rumination by feedlot cattleRumination by feedlot cattle
Diets contained 10% silage Diets contained 10% silage (DM basis)(DM basis)
9.39.3
15.815.8
8.18.1
13.613.6
6.86.8
13.313.3
SilageSilage StrawStraw
SalivationSalivation
• lubrication of feed for lubrication of feed for swallowingswallowing
• passage of feed through the passage of feed through the GI tractGI tract
• buffers (bicarbonate, buffers (bicarbonate, phosphate) acids produced phosphate) acids produced during digestionduring digestion
• enzymic activityenzymic activity– no amylase in ruminantsno amylase in ruminants– pregastric esterase or lipase pregastric esterase or lipase
(preruminant)(preruminant)• nutrients for microbes: mucin, nutrients for microbes: mucin,
P Mg, ClP Mg, Cl
• anti-frothing propertiesanti-frothing properties (bloat)(bloat)
Salivary glands
Parotid saliva: ~ 50 % of total saliva
Amount of SalivaAmount of Saliva
• parotid cannulationparotid cannulation– total collection of salivatotal collection of saliva– only one ductonly one duct
• re-entrant parotid re-entrant parotid cannulationcannulation
• collection at the cardia collection at the cardia using a bagusing a bag– requires partial rumen requires partial rumen
emptyingemptying
SheepSheep
Do animals that eat more Do animals that eat more slowly produce more saliva slowly produce more saliva ??
VFAVFA
Rumen pHRumen pH
particle particle lengthlength
feed digestion
VFA product
ion
saliva
chewingchewing
Effects of level of fiber in the diet Effects of level of fiber in the diet on ruminal pH of dairy cowson ruminal pH of dairy cows