Advance Digestive Physiology (part 1) By: A. Riasi (PhD in Animal Nutrition and Physiology) Http://riasi.iut.ac.ir Isfahan University of Technology.

AdvanceAdvance Digestive Digestive

PhysiologyPhysiology((part 1part 1))

By: A. Riasi (PhD in Animal Nutrition and Physiology)

Http://riasi.iut.ac.ir

Isfahan University of Technology

Development of digestive system

The properties of ruminant’s digestive tracts

Salivation

The receptors

The salivary glands

Control of salivation

The topics

Mastication and swallowing

Rumen and reticulum properties

Characteristics of the preruminant stomach

The wall structure

Development and control of forestomach motility

Blood circulation

Receptors

The topics

Rumination and its components

Attempts to control ruminoreticulum fermentation

Events associated with eructation

Absorption

Urea recycling

The role of thermodynamics in ruminant digestive

The topics

Omasum

Omasal motility

The properties of obomasum

Glands and secretions

Microscopic anatomy

Abomsal motility

The topics

Small intestine

Wall layers

Neuronal network

Blood circulation

Movements control

Transport systems in the epithelia

Entrogastric inhibitory reflex

The topics

Large intestine

Wall properties

Absorption

Motor activity of cecum

Evacuation contractions

Defecation

The topics

References Ruminant Physiology, by Sejrsen et al (2006)

Ruminant Physiology, by Cronje (2000)

Farm Animal Metabolism and Nutrition, by D’Mello

(2000)

Original and review papers

Advantages of pregastric fermentation

Make better use of alternative nutrients

Cellulose

NPN

Ability to detoxify some poisonous compounds

Oxalates, cyanide, alkaloids

Advantages of pregastric fermentation

More effective use of fermentation end products

Volatile fatty acids

Microbial protein

B vitamins

Decrease in handling undigested residues

In wild animals, it allows animals to eat and run

Disadvantages of pregastric fermentation

Fermentation is inefficient

Energy

• Loss Amount (% of total caloric value)

Methane 5-8

Heat of fermentation 5-6


Fermentation is inefficient

Protein

• Some ammonia resulting from microbial degradation will be

absorbed and excreted

• 20% of the nitrogen in microbes is in the form of nucleic

acids


Ruminants are susceptible to ketosis

Ruminants are susceptible to toxins produced

by rumen microbes Nitrates Nitrites

Urea Ammonia

Nonstructural carbohydrates Lactic acid

Tryptophan Methyl indole

Isoflavonoid estrogens Estrogen

Development of digestive systemDevelopment of digestive system

Common Duiker, Deer

Goats, Sheep, Moose

Cattle, Bison


Common Duiker, Deer

Goats, Sheep, Moose

Cattle, Bison


Common Duiker, Deer

Goats, Sheep, Moose

Cattle, Bison


Common Duiker, Deer

Goats, Sheep, Moose

Cattle, Bison

The digestive system of animals has

different function:

Ingestion (eating)

Chewing (mastication)

Swallowing (deglutition)

Absorption of nutrients

Elimination of solid wastes (defecation)

The ruminant digestive tract

The wall of digestive tract as a hollow

organ consisting of several layers:

Mucosa,

Submucosa,

Muscularis externa and

Serosa/adventitia.





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.


The digestive system of ruminant animals

includes the different parts:

Oral cavity

Esophagus

Multi-chambered stomach

Small intestine

Large Intestine


Salivary glands and salivation

◦ Secretions contain:

Enzymes (amylase and lipase)

Water

Glycoproteins

Salivary gland and salivation

Salivary glands and salivation

◦Saliva has secretory IgA, lactoferrin and

lysozyme.

◦Saliva can serve a neutralizing function


The salivary glands have different function

◦ Preparing enzymes

◦ Moistens and lubricates feed

◦ Water balance

◦ Bloat prevention

◦ Recycling of N and minerals including Na, P, and S

◦ Buffer secretion


The architecture

◦Secretory units

Serous

Mucous


◦Ducts

Intercalated

Striated intralobular

Interlobular

Main excretory duct

◦Myoepithelial cells

◦Lymphocytes and plasma cells




In the left panel you see both serous and mucous secretory areas, in among the strands of skeletal muscle in the tongue. At right, a large serous gland is discharging via a duct (D) into the moat (M) around a vallate papilla.


Different kinds of salivary galnds

Parotid

Mandibular

Sublingual

Some minor gland



Salivary flow

◦Saliva production occurring in 2 phases:

Primary secretion

Ductal secretion

◦The salivary ducts rely heavily on the

Na/K/2Cl cotransporter.


Salivary flow

◦The degree of modification of saliva in the

ducts turns heavily on salivary flow rate. Fast rates result in a salivary product more like the

primary secretion.

Slow rates result in an increasingly hypotonic and

potassium rich saliva.

◦Effect of autonomic nervous system


Salivary flow

◦ Ruminant produce a high daily output of saliva.

6 to 16 L/d in sheep

60 to 160 L/d in cattle


Salivary glands Total salivary volumes (L d)

Characteristics Site of reflexogenic stimuli

Parotids

Inferior molars

Palatine, buccal, pharyngealSubmaxillary

Sublingual, labial

3-8

0.7-2

2-6

0.4-0.8

0.1

Serous, isotonic, strongly bufferedSerous, isotonic, strongly bufferedIsotonic, strongly buffered

Mucous, hypotonic, weakly bufferedVery mucous, hypotonic, weakly buffered

Mouth, esophagus, ruminoreticulumMouth, esophagus, ruminoreticulumMouth, esophagus, ruminoreticulumMouth during feeding, not cuddingMouth

Total volume 6-16


Salivary flow◦The secretions from the parotid glands are:

Isotonic with blood plasma,

Have no significant amylase content,

Change their composition in response to salt

depletion,

Have a high alkalinity (pH 8.1)

Recycling the N and P


Salivary flow

◦A 700 kg dairy cow fed a hay-grain diet will

secrete:

190 l saliva/day containing

30-80 gm total N

1100 gm NaHCO3

350 gm Na2HPO4

100 gm NaCl


Control of salivary flow◦A basal level of parotid secretion occurs even

in the totally denervated.

◦Excitation of the secretory (acinar) cells by by

the parasympathetic nerve endings.

◦The increase in parotid blood flow does not

exactly parallel the increase in parotid

secretion.


◦Salivary reflexs are integrated in salivary

centers located in the hindbrain.

◦The buccal mechanoreceptors located in or

near the tooth sockets have major effect.

Chewing of ingesta in cattle may increase salivary

secretion from 2 ml/min to 30 to 50 ml/min.


◦The distension of the esophagus, reticulum,

reticuloomasal orifice, and ruminoreticular

◦Little increase is evoked by lightly stroking the

ruminoreticular epithelium.

◦Reflex increases in salivation may be inhibited

by concurrent stresses and excitement.


◦ Some feeding factors may affect the saliva flow:

Dietary fiber concentration

Forage to grain ratio of the diet

Maturity of the forage

◦ Diet particle size

Grinding

Grain processing by-products

Diet moisture level


Advance Digestive Physiology (part 1) By: A. Riasi (PhD in Animal Nutrition and Physiology) Http://riasi.iut.ac.ir Isfahan University of Technology.

Documents

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bison slide

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