Rumen anatomy Flashcards
What are the components of the ruminant stomach and their basic functions
Rumen - fermentation vat
Reticulum - part of rumen
Omasum - water absorption
Abomasum - true stomach
Why do ruminants have a rem-reticulum + omasum?
Mammals are unable to digest beta-lined polysaccharides (such as cellulose in plants)
The rumen-reticulum + omasum allow utilisation of microorganisms to digest cellulose and hemicellulose
What is the origin of the fore-stomachs of the ruminants
derived from gastric spindle
What is the lining of the forestomachs of ruminants
stratified keratinised epithelium
Why is surgery in ruminants performed on the LHS?
the rumen acts as a plug to prevent abdominal contents from escaping the body cavity
Where is the spleen attached in ruminants?
attached to rumen as greater curvature of the stomach has been lost embryologically
Describe the anatomy of the ruminant oesophagus
Large and distensible
Striated muscle along whole length
Insensitive mucosa
Heavily keratinised
Where does chock (oesophageal obstruction) occur most in ruminants?
close to pharynx at thoracic inlet
Describe the features of the reticulorumen
Watm
Moist
Anaerobic
pH ~6.5
Suitable environment for range of microorganisms
What is the product of fermentation in the reticulorumen
Volatile fatty acids (acetate, butyrate, propionate), CO2 and methane
What happens to the rumen if there is too much grain in diet?
causes rumen acidosis which kilkls off flora
What happens to fibrous feedstuffs in the reticulorumen
They remain long enough for complex carb digestion
Surface area of fibres is increased by initial chewing and ruminating
Long fibre particles are regurgitated and re-chewed
How often are reticulorumen contraction?
~3 every 2 mins
Label the rumen from the LHS
What is the anatomy and function of rumen papillae
Leaf shaped
Keratinised
Poorly developed in roof of dorsal sac
Increased surface area for flora and absorption
How does diet affect the rumen papillae
Long fibres sit at top of rumen -> long papillae
Short fibres sit at bottom of rumen -> short fibre
Gas cap at top of rumen (no fibre) -> no papillae
What stimulates growth rumen papillae?
High conc of VFAs
Long fibres
Which section of the ruminant forstomach is this?
Rumen
Describe the anatomy of the reticulum
Series of cells with smaller cells inside
Small conical papillea
Keratinised
What part of the ruminant forestomach is this?
Reticulum
How does feed quality affect rumination time?
Poor quality feed e.g., rough hay spends more time in the rumen - this is good for the rumen as ruminants are designed to be slow digesters
Grains - spend less time in rumen but leads to acidity problems
What is the function of the omasum?
Still unclear:
- probably water absorption
- pumping ingesta from reticulum into abomasum
Describe the anatomy and function of the omasum
Contains ~100 laminae covered with conical papillae -> huge SA
Laminae are 3 different sizes
Regular contractions squeeze material into recesses and progresses fluid forward
Water reabsorption
Which part of the ruminant forestomach is this?
omasum
Describe the anatomy of the abomasum of ruminants
large longitudinal rugae
columnar epithelium
essentially the same as a monogastric stomach
What part of the ruminant is this
abomasum
How does the neonatal ruminant digest milk?
Digested in the abomasum
Fundic glands produce renin which coagulates casein (milk protein) in acidic environments
The clot retains milk to allow complete digestion by pepsin
How does milk bypass the reticulo-rumen in neonates?
The reticular groove contracts creating a tunnel between oesophagus and reticulo-omasal orifice
When relaxed the oesophagus empties into reticulo-rumen
Only functions when drinking milk
What happen if the reticular groove fails?
Milk enters reticulo-rumen
Milk ferments and causes scour
what is the reticular-groove reflex stimulated by and what is it poorly reactive to?
Stimulated by the vagus nerve due to:
- suckling milk/pharyngeal stimulation
- noises associated with the ‘feeding routine’
Poorly reactive to:
- drinking (hence bucket-fed calves are prone to scour
- stomach tubing
Describe the development of the ruminant forstomach after birth
- development after birth promoted by presence of forage in rumen as young animals start to eat solid food
- rumen flora develops within a couple weeks and is functional by 6-8 weeks
