Digestive System

Ruminants

The only way of finding the limits of the possible is by going beyond them into

the impossible.Arthur C. Clarke

Dentition - Cattle

IncisorsPre-molarsMolars

Deciduous: 20 (there are no deciduous molar and deciduous PM1)

0 0 3 (I C PM) 3 1 3

Permanent: 32 (No PM1) 0 0 3 33 1 3 3

Eruption – Deciduous Teeth

Teeth Age at eruption

1st Incisor (Di 1) Birth – 2 weeks

2nd Incisor (Di 2) Birth – 2 weeks

3rd Incisor (Di 3) Birth – 2 weeks

4th Incisor (Di 4 or C) Birth – 2 weeks

1st Cheek Tooth (Dp 2) Birth to few days of age

2nd Cheek Tooth (Dp 3) Birth to few days of age

3rd Cheek Tooth (Dp 4) Birth to few days of age

Deciduous

Permanent

Eruption – Permanent teeth

Teeth Age at eruption

I 1 18 – 24 months

I 2 24 – 30 months

I 3 36 months

I4 or C 42 – 48 months

1st cheek tooth P2 24 – 30 months

P3 second cheek tooth 18 – 30 months

P4 third cheek tooth 30 – 36 months

M2 fifth cheek tooth 24 – 30 months

M3 sixth cheek tooth 24 – 30 months

Cattle - Dentition

• 14 months: – complete deciduous– short and broad– bright ivory color– space between Di 1 incisors

How old?

•Teeth are longer and narrower•Not touching at upper corner

Rostral Rostral - lateral

How old?

Eruption of one or more central incisors

How old?

At least one of2nd pair of incisors

How old?

I3: 36 months, I4: 42 months

Peg teeth

Dentition – Sheep and Goats

• 2 (0/4 incisors, 3/3 pre-molars, 3/3 molars) = 32

• Animal under one year old: no permanent teeth

• One year old (2 permanent teeth)• Two years old (4 permanent teeth)• Three years old (6 permanent teeth)• Four years old (8 permanent teeth)• Old animal, more than four years old

Permanent Tooth Eruption

• Incisor (I1)1-1.5 years • Incisor (I2)1.5-2 years• Incisor (I3)2.5-3 years• Incisor (I4)3.5-4 years• Premolars1.5-2 years• Molar (M1)3 months• Molar (M2)9-12 months• Molar (M3)1.5-2 years

How old- Sheep?

Wide spacing Broken mouth

How old - Goats

Deciduous – 2 weeks Deciduous – 10 months

1.5 – 2 yrs 3 yrs10 yrs

Digestive System

• Cranial fermentors– Forestomach– E.g. cattle, sheep and deer – digest and extract energy from

cellulose– utilize the protein from fermentative

microbes

• Caudal fermentors• Cecal digestors • E.g. horses and rabbits• digest and extract energy from cellulose • utilize dietary hexose sources directly

Digestive system calf

• Esophageal groove– first few weeks of life,

the rumen, reticulum, and omasum are undeveloped

– By pass reticulum and rumen and goes directly into abomasum

– Grain and forage for rumen development ~ 3 weeks age

Fermentation Ecology• Rumen inoculation

– 1 ml of rumen content: ~10 to 50 billion bacteria,1 million protozoa, variable numbers of yeasts and fungi

– Cellulolytic (digest cellulose) – Hemicellulolytic (digest

hemicellulose) – Amylolytic (digest starch) – Proteolytic (digest proteins) – Sugar utilizing (utilize

monosaccharides and disaccharides)

– Acid utilizing (utilize such substrates as lactic, succinic and malic acids)

– Ammonia producers – Vitamin synthesizers: vitamin B

and K– Methane producers

Entodinium (Rumen Protozoa)

Symbiotic Relationship

• Microbes provide to the ruminant– Digestion of cellulose and hemicellulose– Provision of high quality protein– Production of VFA– Provision of B vitamins– Detoxification of toxic compounds

• Ruminants provide to microbes– Housing– Garbage removal– Nutrients– Optimal environment for growth

Fermentation Ecology

• Rumen pH between 6 and 7

• Grain engorgement: pH <5.5– protozoal populations decrease

• Products: Sugars -> VFA’s– acetic, propionic and butyric acids

Volatile Fatty Acids• Acetic acid

– is utilized minimally in the liver– oxidized throughout most of the body

to generate ATP– Major source of acetyl CoA for

synthesis of lipids. • Proprionic acid

– is almost completely removed from portal blood by the liver

– In the liver, proprionate serves as a major substrate for gluconeogenesis, which is absolutely critical to the ruminant because almost no glucose reaches the small intestine for absorption.

• Butyric acid, – most of which comes out of the rumen

as the ketone beta-hydroxybutyric acid– is oxidized in many tissues for energy

production.

Ruminant Anatomy

• the rumen or paunch• reticulum or

"honeycomb," • the omasum or “book," • the abomasum or "true

stomach." • Esophagus > reticulum

> rumen > omasum > abomasum

• CD

Reticulum – ‘honeycomb’

• Lies against the diaphragm

• rumino-reticulum connected by tissue

• Heavy objects fall– Hardware disease

(traumatic reticuloperitonitis)

• No enzyme secretion• Formation of food bolus

Rumen – ‘Paunch’

• largest of the forestomaches

• sacculated by muscular pillars: dorsal, ventral, caudodorsal and caudoventral sacs

• stratified squamous epithelium (Papillae lining)

• fermentation vat (25 gallons, anaerobic bacteria)

• Absorbs most VFA• Healthy cows: 1-2

minutes/contractions

Omasum - book

• broad longitudinal folds or leaves

• Absorption of water• Reduce particle size,

ingesta between the leaves will be drier than in other compartments

Abomasum – true stomach

– This is the only compartment (also called the true stomach) with a glandular lining

– HCL and digestive enzymes (proteolytic enzymens: mucin, pepsinogen, renin, lipase), needed for the breakdown of feeds, are secreted into the abomasum

– PH decreases from 6 > 2.5• Denatures proteins• Kills bacteria and pathogens• Dissolves minerals

Digestive system - Ruminants• The small intestine

– measures about 20 times the length of the animal– duodenum, jejunum, and ileum. – secretions of the pancreas and the gallbladder, which aid digestion– Most of the digestive process is completed here, and many nutrients are

absorbed through the villi (small finger-like projections) into the blood and lymphatic systems.

• Cecum– junction of the SI and LI, where some previously undigested fiber may be broken

down – Function of cecum?

• Large intestine– last segment of the tract through which undigested feedstuffs pass – absorption of water is the primary digestive activity occurring in the large

intestine– Some bacterial digestion of undigested feed occurs

Function of digestive tract• Eructation (belching)

– Large quantities of gas, mostly carbon dioxide and methane, are produced in the rumen

• Rumination (4 phases)– 35 to 40 percent of each day ruminating (cud chewing)– During rest periods, feed boluses (cud) are regurgitated for rechewing to reduce

particle size and for resalivation. – Feed is more readily digested by rumen microbes as particle size is reduced– Redeglutition: swallowing

Four Steps of Rumination

• Regurgitation– Reverse peristalsis carries food to mouth

• Remastication– Liquid squeezed from bolus and

swallowed– Bolus chewed

• Reinsalivation– Adding more saliva

• Redeglutition– Swallowing bolus and liquids

Remastication and Redeglutition

Digestive system - Ruminants• Motility of the rumen and reticulum

– contractions mix the rumen contents, bring microbes in contact with new feedstuffs, reduce flotation of solids, and move materials out of the rumen

• Saliva production – 50 to 80 quarts of saliva – provides liquid for the microbial population, recirculates nitrogen and minerals,

and buffers the rumen – buffer for helping to maintain a rumen pH between 6.2 and 6.8 for optimum

digestion of forages and feedstuffs • Vomiting

– Rare: suspect toxins

References

• Large Animal Clinical Procedures, Elizabeth Hanie. 2006• http://www.fsis.usda.gov/ofo/tsc/bse_information.htm• http://www.fao.org/docrep/t0690e/t0690e05.htm• http://www.infovets.com/books/smrm/C/C015.htm• http://www.vivo.colostate.edu/hbooks/pathphys/

digestion/herbivores/index.html• http://www.extension.umn.edu/distribution/

livestocksystems/components/di0469-02.html• faculty.fortlewis.edu/LASHELL_B/Nutr2-Rumdigestion.pdf

• http://www.das.psu.edu/research-extension/dairy/nutrition/calves/rumen

• http://www.pitt.edu/~super1/lecture/lec30761/006.htm