By: A. Riasi (PhD in Animal Nutrition & Physiology) Advanced Digestive Physiology (part 2) Isfahan University of Technology Isfahan,

By: A. Riasi (PhD in Animal Nutrition &

Physiology)http://riasi.iut.ac.ir

Advanced Digestive Physiology

)part 2(

Isfahan University of TechnologyIsfahan, Iran

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.

Esophagus

The ruminant stomach and its development


The wall of stomach is made of 4 layers:

• T. Mucosa

• T. Submucosa

• T. Mascularis

• T. Serosa


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.

1

2

3

4

5


Preruminant stomach and food digestion

The calf is a monogastric (birth - about 2 weeks).

The abomasums is actively involved in digestion.

Readily fermentable carbohydrates are important for

the rumen development.


Size of ruminant stomach compartment



Coming from esophagus

Leading to omasum

Pre-ruminant period


Transition from pre-ruminant to ruminant

Absorptive surface area is enhanced by

increasing:

• Papillae length

• Papillae width

• Papillae density


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)


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)


Undeveloped Rumen Developed Rumen


Milk only Milk and grain Milk and hay

Importance of diet to rumen development (6 weeks of age)


Milk and hayMilk, hay and grain


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.


At birth day the rumen is sterile

• Aerobic bacteria

• Change of bacteria population


Prolonged milk feeding may retard:

• Typical ruminal microflora

• Establishment of protozoa


Factors may affect calf’s rumen microflora

• Feeds

• Environment

• Bedding

• Hair


The numbers of total bacteria

Change in types of bacteria by feeding

DM:

• Decreasing aerobic bacteria

• Increasing anaerobic bacteria


Establishing a rumen microflora


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.

Liquids in the rumen

Measures of ruminal activity:

• Rumen contractions

• Rumen pressure

• Regurgitation (cud chewing)

Little muscular activity at birth.


Solid feed intake stimulates:

• Rumen microbial proliferation

• Production of microbial end products


Effect of chemical composition of concentrates:

• A shift in the microbial population

• Increasing butyrate and propionate production at the

expense of acetate.


Forages, have an increased ability to

maintain a higher ruminal pH, due to:

• A larger particle size

• An increased fiber content



1393برگرفته از میرزایی و همکاران،

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 most readily

absorbed by rumen epithelium.

Absorptive ability of the rumen tissue

The primary factor determining ruminal

development is dry feed intake.

• Starter

• Proper stimulation for rumen development

Availability of substrate

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 by papillae degeneration and

sloughing.

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.

Rumen parakeratosis

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.

Changes in rumen muscularization

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

Physiology and ontogeny of rumen development

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.


Some hormones and growth factors may

have mediator effect:

• Insulin, Pentagastrin, Glucagon

• IGF-1, Epidermal growth factor

• Cortisol


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-3-

methylglutaryyl-CoA synthase.

Neonatal ruminal epithelial metabolism

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.


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


A rapid increase in activity of hepatic

gluconeogenic enzymes:

• Glucose 6-phosphatase activity having been shown to

double during this period


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


Clostridium perfringens types A, B, C

Clostridia are normally found in the

intestine of cattle and can survive for months

in the soil.


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


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


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


Documents

By: A. Riasi (PhD in Animal Nutrition & Physiology) Advanced Digestive Physiology (part 2) Isfahan University of Technology Isfahan,